Save 6 seconds when starting dev server (#2230)

package.json

@@ -17,8 +17,8 @@
     "stop-emulator": "curl -X POST 'http://localhost:15606/shutdown'",
     "build": "gulp",
     "watch": "gulp watch",
-    "start-app": "npm run build && ./scripts/start_server.sh",
-    "start": "source cs-env/bin/activate; (npm run start-emulator-persist > /dev/null 2>&1 &); sleep 6; curl --retry 4 http://localhost:15606/ --retry-connrefused; npm run start-app; status=$?; npm run stop-emulator; exit $status",
+    "start-app": "npm run build && curl --retry 4 http://localhost:15606/ --retry-connrefused && ./scripts/start_server.sh",
+    "start": "source cs-env/bin/activate; (npm run start-emulator-persist > /dev/null 2>&1 &); npm run start-app; status=$?; npm run stop-emulator; exit $status",
     "stop": "killall cs-env/bin/python3.9",
     "test": "(npm run start-emulator > /dev/null 2>&1 &); sleep 6; curl --retry 4 http://localhost:15606/ --retry-connrefused; npm run do-tests; status=$?; npm run stop-emulator; exit $status",
     "webtest": "web-test-runner \"static/**/*_test.js\" --node-resolve --playwright --browsers chromium firefox",