Fix create disk pool dir
Fix create disk pool dir

The install.disk.pool dir can be any dir.
So creating this dir can be problematic especially regarding
user permissions. User should be responsible to create that dir
if he is using --disk-pool option

Change-Id: I7e6b77c1373aecde494a52889b848a7486800523

redhat-openstack/infrared,redhat-openstack/infrared,redhat-openstack/infrared