Add integration test and/or example consuming remote tags

[codefromthecrypt]

Right now, all the RPC views use tags local to the process. For integration concerns, we should have a test that consumes for example the incoming client method tag. Otherwise remote propagation errors might go unnoticed.

See https://github.com/census-instrumentation/opencensus-specs/blob/master/stats/gRPC.md#why-different-tag-name-for-serverclient-method https://github.com/census-instrumentation/opencensus-java/blob/master/contrib/grpc_metrics/src/main/java/io/opencensus/contrib/grpc/metrics/RpcViewConstants.java