rgw: create thread_pipe before RGWHTTPManager::ReqsThread

closes a potential race between pipe creation and
RGWHTTPManager::reqs_thread_entry()'s access of thread_pipe

Signed-off-by: Casey Bodley <cbodley@redhat.com>

src/rgw/rgw_http_client.cc

@@ -694,16 +694,16 @@ int RGWHTTPManager::complete_requests()
 
 int RGWHTTPManager::set_threaded()
 {
-  is_threaded = true;
-  reqs_thread = new ReqsThread(this);
-  reqs_thread->create("http_manager");
-
   int r = pipe(thread_pipe);
   if (r < 0) {
     r = -errno;
     ldout(cct, 0) << "ERROR: pipe() returned errno=" << r << dendl;
     return r;
   }
+
+  is_threaded = true;
+  reqs_thread = new ReqsThread(this);
+  reqs_thread->create("http_manager");
   return 0;
 }