change to zero exit if target app disconnects

Summary: Per yesterdays review, consider target app exiting as  a signal to end the dump process.

Reviewed By: passy

Differential Revision: D31609065

fbshipit-source-id: fbd92f6c5344245d0bdae3f21be1a5d235aa1fa1

desktop/flipper-dump/src/index.tsx

@@ -169,7 +169,9 @@ async function start(deviceTitle: string, appName: string, pluginId: string) {
 
     server.on('client-disconnected', ({id}) => {
       if (id === client?.id) {
-        reject(new Error('Application disconnected'));
+        // TODO: maybe we need a flag to signal that this might be undesired?
+        logger.info('Target application disconnected, exiting...');
+        process.exit(0);
       }
     });