Integration tests: Use testing.T logger through zap for grpc#12781

Merged

ptabor merged 2 commits intoetcd-io:masterfrom ptabor:20210315-flaki-balancer

Mar 18, 2021

+62-71

Commits on Mar 16, 2021

Integration with grpc-settable logger.
ptabor
committed

Commits on Mar 17, 2021

Enable configuring delegated zap-logging for embed server.
ptabor
committed