Comment 5 for bug 1562258

Got the trace back stack as below, so we need to change this call path to avoid load manager first than conf.

Traceback (most recent call last):
  File "/usr/local/bin/ironic-conductor", line 6, in <module>
    from ironic.cmd.conductor import main
  File "/opt/stack/ironic/ironic/cmd/conductor.py", line 29, in <module>
    from ironic.common import service as ironic_service
  File "/opt/stack/ironic/ironic/common/service.py", line 29, in <module>
    from ironic.api import app
  File "/opt/stack/ironic/ironic/api/app.py", line 25, in <module>
    from ironic.api import hooks
  File "/opt/stack/ironic/ironic/api/hooks.py", line 24, in <module>
    from ironic.conductor import rpcapi
  File "/opt/stack/ironic/ironic/conductor/rpcapi.py", line 29, in <module>
    from ironic.conductor import manager
  File "/opt/stack/ironic/ironic/conductor/manager.py", line 55, in <module>
    from oslo_service import periodic_task