test: fix flaky grpclb TestDropRequest (#2865)
test: fix flaky grpclb TestDropRequest (#2865)


dfawley/grpc-go,stanley-cheung/grpc-go,dfawley/grpc-go,stanley-cheung/grpc-go,menghanl/grpc-go,grpc/grpc-go,grpc/grpc-go,menghanl/grpc-go