Chained user switching with password change

build/tfs/linux/smoketest.sh

@@ -26,8 +26,7 @@ step "Build minified" \
 	npm run gulp -- --max_old_space_size=4096 "vscode-linux-$ARCH-min"
 
 step "Configure environment" \
-	id -u testuser || (useradd -m testuser; chpasswd <<< testuser:testpassword)
-	su testuser
+	id -u testuser || (useradd -m testuser; chpasswd <<< testuser:testpassword); su testuser
 	cd $BUILD_REPOSITORY_LOCALPATH
 	git config --global user.name "Michel Kaporin"
 	git config --global user.email "monacotools@microsoft.com"