Merge pull request #11787 from guantaol/qps_driver

src/proto/grpc/testing/control.proto

test/cpp/qps/BUILD

test/cpp/qps/client.h

test/cpp/qps/driver.cc

test/cpp/qps/driver.h

test/cpp/qps/qps_json_driver.cc

test/cpp/qps/qps_openloop_test.cc

test/cpp/qps/qps_worker.cc

test/cpp/qps/qps_worker.h

test/cpp/qps/report.cc

test/cpp/qps/report.h

test/cpp/qps/secure_sync_unary_ping_pong_test.cc

test/cpp/qps/server.h

test/cpp/qps/worker.cc

test/cpp/util/create_test_channel.cc

test/cpp/util/create_test_channel.h