raw_template_files_get always use context session
raw_template_files_get always use context session

It is now always called with an admin context so it won't be None

Change-Id: Ic8924b01b36933b1ce162484092bf3677f7ce13b
Related-Bug: #1479723

openstack/heat,noironetworks/heat,openstack/heat,noironetworks/heat