grpc_logrus uses deprecated function grpclog.SetLogger

[at-ishikawa]

Summary

LoggerV2 in grpclog package reads the environment variables GRPC_GO_LOG_SEVERITY_LEVEL, and GRPC_GO_LOG_VERBOSITY_LEVEL and enable to suppress to output some unimportant logs.
But, grpc_logrus.ReplaceGrpcLogger depends on deprecated function grpclog.SetLogger, which outputs any logs in gRPC.
Because of this, we can't control which severity or which verbosity level is outputted.

Sample logs by this function

{"level":"info","msg":"ccResolverWrapper: sending new addresses to cc: [{cloudtrace.googleapis.com:443 0  \u003cnil\u003e}]","system":"system","time":"2018-12-09T14:05:48+09:00"}
{"level":"info","msg":"ClientConn switching balancer to \"pick_first\"","system":"system","time":"2018-12-09T14:05:48+09:00"}
{"level":"info","msg":"pickfirstBalancer: HandleSubConnStateChange: 0xc4200302c0, CONNECTING","system":"system","time":"2018-12-09T14:05:48+09:00"}
{"level":"info","msg":"pickfirstBalancer: HandleSubConnStateChange: 0xc4200302c0, READY","system":"system","time":"2018-12-09T14:05:49+09:00"}
{"level":"info","msg":"pickfirstBalancer: HandleSubConnStateChange: 0xc42049e060, READY","system":"system","time":"2018-12-09T14:05:49+09:00"}