Add missing import for TRANSITIONAL_STATES and ERROR in dbusrole.py

If roled is started with an instance it fails with 'TRANSITIONAL_STATES' is not
defined.

Fixes: #52

Reviewed at https://reviewboard-fedoraserver.rhcloud.com/r/224/

src/rolekit/server/dbusrole.py

@@ -30,7 +30,7 @@
 import slip.dbus.service
 
 from rolekit import async
-from rolekit.config import ETC_ROLEKIT_ROLES
+from rolekit.config import ETC_ROLEKIT_ROLES, TRANSITIONAL_STATES, ERROR
 from rolekit.config.dbus import DBUS_INTERFACE_ROLE, DBUS_PATH_ROLES, PK_ACTION_ALL
 from rolekit.logger import log
 from rolekit.server.decorators import dbus_handle_exceptions