read_fd should always have a certain value when create error occurs [fix: while using eventfd, when error occurs during creating eventfd, a random fd will be closed]

src/core/lib/iomgr/wakeup_fd_eventfd.cc

@@ -32,12 +32,11 @@
 #include "src/core/lib/profiling/timers.h"
 
 static grpc_error* eventfd_create(grpc_wakeup_fd* fd_info) {
-  int efd = eventfd(0, EFD_NONBLOCK | EFD_CLOEXEC);
-  if (efd < 0) {
+  fd_info->read_fd = eventfd(0, EFD_NONBLOCK | EFD_CLOEXEC);
+  fd_info->write_fd = -1;
+  if (fd_info->read_fd < 0) {
     return GRPC_OS_ERROR(errno, "eventfd");
   }
-  fd_info->read_fd = efd;
-  fd_info->write_fd = -1;
   return GRPC_ERROR_NONE;
 }