Improve handling of epoch operations in validator-api if there's a connectivity issues

[tommyv1987]

The epoch operation failed due to a connectivity issue:

We need to bulletproof this so this doesn't happen.

thread 'tokio-runtime-worker' panicked at 'called `Result::unwrap()` on an `Err` value: ValidatorClientError(NymdError(TendermintError(HTTP e>
Caused by:
    connection closed before message completed
Location:
    /home/nym/.cargo/registry/src/github.com-1ecc6299db9ec823/flex-error-0.4.4/src/tracer_impl/eyre.rs:10:9)))', validator-api/src/main.rs:58>
stack backtrace:
   0: rust_begin_unwind
             at ./rustc/e092d0b6b43f2de967af0887873151bb1c0b18d3/library/std/src/panicking.rs:584:5
   1: core::panicking::panic_fmt
             at ./rustc/e092d0b6b43f2de967af0887873151bb1c0b18d3/library/core/src/panicking.rs:142:14
   2: core::result::unwrap_failed
             at ./rustc/e092d0b6b43f2de967af0887873151bb1c0b18d3/library/core/src/result.rs:1785:5
   3: <core::future::from_generator::GenFuture<T> as core::future::future::Future>::poll
   4: tokio::runtime::task::core::CoreStage<T>::poll
note: Some details are omitted, run with `RUST_BACKTRACE=full` for a verbose backtrace.