Fix curl thread detach

Author: marcalff

ext/src/http/client/curl/http_client_curl.cc

@@ -462,18 +462,18 @@ void HttpClient::MaybeSpawnBackgroundThread()
             {
               if (self->background_thread_)
               {
+                if (self->background_thread_instrumentation_ != nullptr)
+                {
+                  self->background_thread_instrumentation_->OnEnd();
+                  self->background_thread_instrumentation_.reset();
+                }
                 self->background_thread_->detach();
                 self->background_thread_.reset();
               }
               break;
             }
           }
         }
-
-        if (self->background_thread_instrumentation_ != nullptr)
-        {
-          self->background_thread_instrumentation_->OnEnd();
-        }
       },
       this));
 }