Sporadic failure of OtlpGrpcExporterRetryIntegrationTests.StatusCodes test

[dbarker]

Describe your environment
main at b4328c0

Steps to reproduce

1. build with WITH_OTLP_RETRY_PREVIEW=ON
2. run the otlp grpc exporter test

What is the expected behavior?
test always passes

What is the actual behavior?

test sometimes fails.

Note: Google Test filter = */OtlpGrpcExporterRetryIntegrationTests.StatusCodes/*
[==========] Running 40 tests from 1 test suite.
[----------] Global test environment set-up.
[----------] 40 tests from StatusCodes/OtlpGrpcExporterRetryIntegrationTests
[ RUN      ] StatusCodes/OtlpGrpcExporterRetryIntegrationTests.StatusCodes/0
Error:  File: /home/runner/work/opentelemetry-cpp/opentelemetry-cpp/exporters/otlp/src/otlp_grpc_client.cc:241 [OTLP GRPC Client] ERROR: Export trace span(s) failed with status_code: "14" error_message: "failed to connect to all addresses; last error: UNKNOWN: ipv4:127.0.0.1:4317: Failed to connect to remote host: Connection refused"
Error:  File: /home/runner/work/opentelemetry-cpp/opentelemetry-cpp/exporters/otlp/src/otlp_grpc_exporter.cc:138 [OTLP TRACE GRPC Exporter] ERROR: Export 1 trace span(s) error: 1
/home/runner/work/opentelemetry-cpp/opentelemetry-cpp/exporters/otlp/test/otlp_grpc_exporter_test.cc:553: Failure
Expected equality of these values:
  expected_attempts
    Which is: 5
  service.request_count_
    Which is: 0

[  FAILED  ] StatusCodes/OtlpGrpcExporterRetryIntegrationTests.StatusCodes/0, where GetParam() = (true, { 1 }, 5) (416 ms)

Additional context
There is a race condition between the main test thread and grpc server thread. The main thread can call shutdown before the server is up and able to process messages.