Bug 1355888 - Mark marionette.enabled pref in client as a deprecated; r=whimboo

To preserve backwards compatibility for in-app restarts using
Services.startup.quit(eRestart), we want to continue using the
marionette.enabled preference in the Python client until the patch
introducing the MARIONETTE environment variable (preceding this) makes
it into an official release.

This is due to the fact that the Marionette Python client is being
used for upgrade tests, and it is needs to stay compatible with all
release trains.

MozReview-Commit-ID: KstsJRu4lIP

--HG--
extra : rebase_source : 01a00549a9c8b57fd65aad8cd68ef04fdcca981d

testing/marionette/client/marionette_driver/geckoinstance.py

@@ -73,9 +73,10 @@ class GeckoInstance(object):
         "javascript.options.showInConsole": True,
 
         # Enable Marionette component
+        # (deprecated and can be removed when Firefox 60 ships)
         "marionette.enabled": True,
-        # Deprecated, and can be removed in Firefox 60.0
         "marionette.defaultPrefs.enabled": True,
+
         # Disable recommended automation prefs in CI
         "marionette.prefs.recommended": False,