Longer connection wait time

Summary:
I'm seeing some failures where no client is connected when we do the export.
This increases the wait time before sending the SIGINT.

Reviewed By: passy

Differential Revision: D15716214

fbshipit-source-id: 4646ef9d1c37e491273bd9deff504675b0e4e780

headless-tests/__tests__/headlessIntegrationTests.js

@@ -60,7 +60,7 @@ const runHeadless = memoize((args: Array<string>) => {
 
     setTimeout(() => {
       process.kill('SIGINT');
-    }, 10000);
+    }, 20000);
   });
 });