smoke: fix darwin timing

build/tfs/darwin/smoketest.sh

@@ -21,7 +21,10 @@ step "Install distro dependencies" \
 step "Build minified & upload source maps" \
 	npm run gulp -- vscode-darwin-min
 
+function runSmokeTest {
+	cd $BUILD_SOURCESDIRECTORY/test/smoke && \
+		./node_modules/.bin/mocha --build "$AGENT_BUILDDIRECTORY/VSCode-darwin/Visual Studio Code - Insiders.app/Contents/MacOS/Electron" --screenshot
+}
+
 step "Run smoke test" \
-	pushd test/smoke
-	./node_modules/.bin/mocha --build "$AGENT_BUILDDIRECTORY/VSCode-darwin/Visual Studio Code - Insiders.app/Contents/MacOS/Electron" --screenshot
-	popd
\ No newline at end of file
+	runSmokeTest
\ No newline at end of file