THRIFT-5909: Fixed Thrift::TypeError exception in specs

[kpumuk]

An error occurs while running specs, that changes the behavior of the system under test, leading to false positive:

   NonblockingServer
   Thrift::NonblockingServer
   #<Thread:0x0000ffff67b9f138 /code/lib/rb/spec/nonblocking_server_spec.rb:147 run> terminated with exception (report_on_exception is true):
   /code/lib/rb/lib/thrift/types.rb:69:in 'Thrift.check_type': Expected Types::DOUBLE, received Integer for field seconds (Thrift::TypeError)
          from /code/lib/rb/lib/thrift/struct.rb:157:in 'block in SpecNamespace::NonblockingService::Sleep_args#field_accessor'
          from /code/lib/rb/lib/thrift/client.rb:41:in 'block in Thrift::Client#send_message_args'
          from /code/lib/rb/lib/thrift/client.rb:40:in 'Hash#each'
          from /code/lib/rb/lib/thrift/client.rb:40:in 'Thrift::Client#send_message_args'
          from /code/lib/rb/lib/thrift/client.rb:30:in 'Thrift::Client#send_message'
          from /code/lib/rb/spec/gen-rb/nonblocking_service.rb:75:in 'SpecNamespace::NonblockingService::Client#send_sleep'
          from /code/lib/rb/spec/gen-rb/nonblocking_service.rb:70:in 'SpecNamespace::NonblockingService::Client#sleep'
          from /code/lib/rb/spec/nonblocking_server_spec.rb:160:in 'block in RSpec::ExampleGroups::NonblockingServer::ThriftNonblockingServer#setup_client_thread'
   should kill active messages when they don't expire while shutting down

When an integer 10 is sent to "sleep", instead of actually sleeping an error happens, and the method never called, leading to no record of the method execution recorded in the result. Which is the same expectation is if the method call was aborted in the middle.

Before:

After:

• [x] Did you create an Apache Jira ticket? THRIFT-5909
• [x] If a ticket exists: Does your pull request title follow the pattern "THRIFT-NNNN: describe my issue"?
• [x] Did you squash your changes to a single commit? (not required, but preferred)
• [x] Did you do your best to avoid breaking changes? If one was needed, did you label the Jira ticket with "Breaking-Change"?
• [ ] If your change does not involve any code, include [skip ci] anywhere in the commit message to free up build resources.