[autotest] Remove old priority hack

This is from 2013, Im assuming the priorities have all been migrated
over.

The reason for doing this is that the sole purpose of this function is
to remove invalid keywords from passing locals() to create_job_common,
so this is a step toward removing locals() and this function.

BUG=None
TEST=CQ

Change-Id: Ia5b527b509863bbe12ff047628c23a988dbc32c9
Reviewed-on: https://chromium-review.googlesource.com/420178
Commit-Ready: Allen Li <ayatane@chromium.org>
Tested-by: Allen Li <ayatane@chromium.org>
Reviewed-by: Prathmesh Prabhu <pprabhu@chromium.org>
diff --git a/server/frontend.py b/server/frontend.py
index 35ec648..f5d9899 100644
--- a/server/frontend.py
+++ b/server/frontend.py
@@ -25,6 +25,7 @@
 from autotest_lib.frontend.afe import rpc_client_lib
 from autotest_lib.client.common_lib import control_data
 from autotest_lib.client.common_lib import global_config
+from autotest_lib.client.common_lib import priorities
 from autotest_lib.client.common_lib import utils
 from autotest_lib.tko import db
 
@@ -653,8 +654,10 @@
                         success=success)
 
 
-    def create_job(self, control_file, name=' ', priority='Medium',
-                control_type=control_data.CONTROL_TYPE_NAMES.CLIENT, **dargs):
+    def create_job(self, control_file, name=' ',
+                   priority=priorities.Priority.DEFAULT,
+                   control_type=control_data.CONTROL_TYPE_NAMES.CLIENT,
+                   **dargs):
         id = self.run('create_job', name=name, priority=priority,
                  control_file=control_file, control_type=control_type, **dargs)
         return self.get_jobs(id=id)[0]