Bug 1293426 - Allow TPS config to specify preference values so it can be pointed at non-production servers r=markh

MozReview-Commit-ID: 8NDJwIaurVF

--HG--
extra : rebase_source : 05df5a1383d9194100159e2275971803b757b45b

testing/tps/tps/testrunner.py

@@ -371,6 +371,9 @@ class TPSTestRunner(object):
         if self.debug:
             self.preferences.update(self.debug_preferences)
 
+        if 'preferences' in self.config:
+            self.preferences.update(self.config['preferences'])
+
     def run_tests(self):
         # delete the logfile if it already exists
         if os.access(self.logfile, os.F_OK):