geckodriver: marionette: set marionette.port in profile

The marionette.defaultPrefs.port preference
has been renamed to marionette.port as part of
https://bugzilla.mozilla.org/show_bug.cgi?id=1344748.

We keep the fallback preference around until Firefox 54 becomes stable
for backwards compatibility reasons.

Source-Repo: https://github.com/mozilla/geckodriver
Source-Revision: 8f19dc4dac63da4153584a2a6974c26be9453ecc

committer: jgraham <james@hoppipolla.co.uk>

--HG--
extra : rebase_source : c47f609e17ce7310c48f801bd85c9291dfb4b88a

testing/geckodriver/src/marionette.rs

@@ -355,6 +355,8 @@ impl MarionetteHandler {
             prefs.insert("marionette.logging", Pref::new(level.to_string()));
         };
 
+        // fallback can be removed when Firefox 54 becomes stable
+        prefs.insert("marionette.port", Pref::new(port as i64));
         prefs.insert("marionette.defaultPrefs.port", Pref::new(port as i64));
 
         prefs.write().map_err(|_| WebDriverError::new(ErrorStatus::UnknownError,