android_interop_testing frequently failing

[ejona86]

We used to see infrastructure failures, but it seems those have gone away. Now I'm seeing timeouts after 60 seconds, which doesn't give us much to go on.

We are hitting a live server (grpc-test.sandbox.googleapis.com). I wonder if we should instead start a local server, now that we have OkHttp server available. I found one clear example of network connectivity being a problem "ConnectException: Connection timed out".

The failure is generally for the Nexus6P. And API levels 29 and 30 from #10461 see frequent failures.

[ejona86]

Note: it looks like we don't enable keepalive. Although it'd have to probably be fairly aggressive to be able to help.
https://github.com/grpc/grpc-java/blob/1d03bb80a9e45c3f0ff542703bae497dac11e218/android-interop-testing/src/androidTest/java/io/grpc/android/integrationtest/InteropInstrumentationTest.java#L116C15-L116C41

But it also looks like we create a new Channel for each test... and we don't shut down the channel.