Merge pull request #3001 from yang-g/temp_str

Bug fix. Called c_str on a temp string

src/cpp/client/channel.cc

@@ -71,7 +71,7 @@ Call Channel::CreateCall(const RpcMethod& method, ClientContext* context,
   } else {
     const char* host_str = NULL;
     if (!context->authority().empty()) {
-      host_str = context->authority().c_str();
+      host_str = context->authority_.c_str();
     } else if (!host_.empty()) {
       host_str = host_.c_str();
     }