Add action return values

[lukicmarko]

Add action return values in order to use it in Fastfile

result = run_tests_firebase_testlab(
        project_id: "projectid",
        model: "Nexus6P,sailfish,victara",
        version: "27,28,19",
        locale: "en_US,en_US,en_US",
        orientation: "portrait,portrait,portrait",
        gcloud_service_key_file: "key.json",
        app_apk:"./app-staging-debug.apk",
        android_test_apk:"./app-staging-debug-androidTest.apk",
        output_dir: "./instrumentationStagingTestResults")

        puts result["result_bucket_url"]
        puts result["test_lab_console_url"]
        puts result["test_failed"]