Replace IO.select with IO#wait_* when checking a single IO

[MSP-Greg]

Description

Replace IO.select with IO#wait_readable/IO#wait_writable when checking a single IO.

This changed an intermittent macOS issue into something stable, which was an Errno::EPIPE error being raised when a client writes to a UNIXSocket, and the server is closing. Fixed in test file.

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[MSP-Greg]

TestIntegrationPumactl#test_phased_restart_cluster failed in one job (Ubuntu 18.03, Ruby 2.7), it has an assert for total time taken to restart and also stop. Darwin value is 8, Ubuntu is 5. It took about 5.5. It is Friday afternoon in the US, and CI is often busy.

Maybe the time should be increased to 6?

[dentarg]

Maybe the time should be increased to 6?

Sure... do we need this to take a certain amount of time? I guess we want to catch it taking unreasonable amount of time. Maybe make it 10 seconds (or more?) for all?

[ioquatix]

Nice work.