Create conf directory during devstack install phase
Create conf directory during devstack install phase

Otherwise other plugins which depend on aodh and want to set
configuration items may have issues with the configuration directory not
being there.

Change-Id: I2e60ed0af6e1b18bbb65e17007e3b2e14ff44b04

openstack/aodh,pczerkas/aodh,openstack/aodh,pczerkas/aodh