Merge pull request #1036 from zyearn/fix_grpc_ut

fix grpc ut
diff --git a/src/brpc/policy/http_rpc_protocol.cpp b/src/brpc/policy/http_rpc_protocol.cpp
index 3776109..734eb0f 100644
--- a/src/brpc/policy/http_rpc_protocol.cpp
+++ b/src/brpc/policy/http_rpc_protocol.cpp
@@ -583,7 +583,7 @@
             hreq.SetHeader(common->TE, common->TRAILERS);
             if (cntl->timeout_ms() >= 0) {
                 hreq.SetHeader(common->GRPC_TIMEOUT,
-                        butil::string_printf("%" PRId64, cntl->timeout_ms()));
+                        butil::string_printf("%" PRId64 "m", cntl->timeout_ms()));
             }
             // Append compressed and length before body
             AddGrpcPrefix(&cntl->request_attachment(), grpc_compressed);