Test failure in `disable_keep_alive_mid_request`

[cratelyn]

It seems that disable_keep_alive_mid_request sometimes fails too.

https://github.com/tokio-rs/tokio/actions/runs/17503750269/job/49722717146

failures:

---- disable_keep_alive_mid_request stdout ----

thread '<unnamed>' panicked at tests/server.rs:1205:9:
should receive OK response, but buf: []
stack backtrace:
   0: __rustc::rust_begin_unwind
             at /rustc/29483883eed69d5fb4db01964cdf2af4d86e9cb2/library/std/src/panicking.rs:697:5
   1: core::panicking::panic_fmt
             at /rustc/29483883eed69d5fb4db01964cdf2af4d86e9cb2/library/core/src/panicking.rs:75:14
   2: server::disable_keep_alive_mid_request::{{closure}}::{{closure}}
             at ./tests/server.rs:1205:9
note: Some details are omitted, run with `RUST_BACKTRACE=full` for a verbose backtrace.

thread 'disable_keep_alive_mid_request' panicked at tests/server.rs:1235:18:
called `Result::unwrap()` on an `Err` value: Any { .. }
stack backtrace:
   0: __rustc::rust_begin_unwind
             at /rustc/29483883eed69d5fb4db01964cdf2af4d86e9cb2/library/std/src/panicking.rs:697:5
   1: core::panicking::panic_fmt
             at /rustc/29483883eed69d5fb4db01964cdf2af4d86e9cb2/library/core/src/panicking.rs:75:14
   2: core::result::unwrap_failed
             at /rustc/29483883eed69d5fb4db01964cdf2af4d86e9cb2/library/core/src/result.rs:1761:5
   3: core::result::Result<T,E>::unwrap
             at /rustc/29483883eed69d5fb4db01964cdf2af4d86e9cb2/library/core/src/result.rs:1167:23
   4: server::disable_keep_alive_mid_request::{{closure}}
             at ./tests/server.rs:1235:18
   5: <core::pin::Pin<P> as core::future::future::Future>::poll
             at /rustc/29483883eed69d5fb4db01964cdf2af4d86e9cb2/library/core/src/future/future.rs:124:9
   6: <core::pin::Pin<P> as core::future::future::Future>::poll
             at /rustc/29483883eed69d5fb4db01964cdf2af4d86e9cb2/library/core/src/future/future.rs:124:9
   7: tokio::runtime::scheduler::current_thread::CoreGuard::block_on::{{closure}}::{{closure}}::{{closure}}
             at /Users/runner/work/tokio/tokio/tokio/src/runtime/scheduler/current_thread/mod.rs:742:70
   8: tokio::task::coop::with_budget
             at /Users/runner/work/tokio/tokio/tokio/src/task/coop/mod.rs:167:5
   9: tokio::task::coop::budget
             at /Users/runner/work/tokio/tokio/tokio/src/task/coop/mod.rs:133:5
  10: tokio::runtime::scheduler::current_thread::CoreGuard::block_on::{{closure}}::{{closure}}
             at /Users/runner/work/tokio/tokio/tokio/src/runtime/scheduler/current_thread/mod.rs:742:25
  11: tokio::runtime::scheduler::current_thread::Context::enter
             at /Users/runner/work/tokio/tokio/tokio/src/runtime/scheduler/current_thread/mod.rs:432:19
  12: tokio::runtime::scheduler::current_thread::CoreGuard::block_on::{{closure}}
             at /Users/runner/work/tokio/tokio/tokio/src/runtime/scheduler/current_thread/mod.rs:741:44
  13: tokio::runtime::scheduler::current_thread::CoreGuard::enter::{{closure}}
             at /Users/runner/work/tokio/tokio/tokio/src/runtime/scheduler/current_thread/mod.rs:829:68
  14: tokio::runtime::context::scoped::Scoped<T>::set
             at /Users/runner/work/tokio/tokio/tokio/src/runtime/context/scoped.rs:40:9
  15: tokio::runtime::context::set_scheduler::{{closure}}
             at /Users/runner/work/tokio/tokio/tokio/src/runtime/context.rs:176:38
  16: std::thread::local::LocalKey<T>::try_with
             at /rustc/29483883eed69d5fb4db01964cdf2af4d86e9cb2/library/std/src/thread/local.rs:315:12
  17: std::thread::local::LocalKey<T>::with
             at /rustc/29483883eed69d5fb4db01964cdf2af4d86e9cb2/library/std/src/thread/local.rs:279:20
  18: tokio::runtime::context::set_scheduler
             at /Users/runner/work/tokio/tokio/tokio/src/runtime/context.rs:176:17
  19: tokio::runtime::scheduler::current_thread::CoreGuard::enter
             at /Users/runner/work/tokio/tokio/tokio/src/runtime/scheduler/current_thread/mod.rs:829:27
  20: tokio::runtime::scheduler::current_thread::CoreGuard::block_on
             at /Users/runner/work/tokio/tokio/tokio/src/runtime/scheduler/current_thread/mod.rs:729:24
  21: tokio::runtime::scheduler::current_thread::CurrentThread::block_on::{{closure}}
             at /Users/runner/work/tokio/tokio/tokio/src/runtime/scheduler/current_thread/mod.rs:200:33
  22: tokio::runtime::context::runtime::enter_runtime
             at /Users/runner/work/tokio/tokio/tokio/src/runtime/context/runtime.rs:65:16
  23: tokio::runtime::scheduler::current_thread::CurrentThread::block_on
             at /Users/runner/work/tokio/tokio/tokio/src/runtime/scheduler/current_thread/mod.rs:188:9
  24: tokio::runtime::runtime::Runtime::block_on_inner
             at /Users/runner/work/tokio/tokio/tokio/src/runtime/runtime.rs:356:52
  25: tokio::runtime::runtime::Runtime::block_on
             at /Users/runner/work/tokio/tokio/tokio/src/runtime/runtime.rs:330:18
  26: server::disable_keep_alive_mid_request
             at ./tests/server.rs:1235:26
  27: server::disable_keep_alive_mid_request::{{closure}}
             at ./tests/server.rs:1191:42
  28: core::ops::function::FnOnce::call_once
             at /rustc/29483883eed69d5fb4db01964cdf2af4d86e9cb2/library/core/src/ops/function.rs:250:5
  29: core::ops::function::FnOnce::call_once
             at /rustc/29483883eed69d5fb4db01964cdf2af4d86e9cb2/library/core/src/ops/function.rs:250:5
note: Some details are omitted, run with `RUST_BACKTRACE=full` for a verbose backtrace.

Originally posted by @mox692 in #3896