Mach update-wpt shoudl default to "--no-patch"

Change mach default behavior for update-wpt to "--no-patch" provide an
alternate option "--patch" for anyone who does want this behavior

python/servo/testing_commands.py

@@ -360,9 +360,12 @@ def wptrunner(self, run_file, **kwargs):
              description='Update the web platform tests',
              category='testing',
              parser=updatecommandline.create_parser())
-    def update_wpt(self, **kwargs):
+    @CommandArgument('--patch', action='store_true', default=False,
+                     help='Create an mq patch or git commit containing the changes')
+    def update_wpt(self, patch, **kwargs):
         self.ensure_bootstrapped()
         run_file = path.abspath(path.join("tests", "wpt", "update.py"))
+        kwargs["no_patch"] = not patch
         run_globals = {"__file__": run_file}
         execfile(run_file, run_globals)
         return run_globals["update_tests"](**kwargs)