Add OpenStack-image-import-methods header
Add OpenStack-image-import-methods header

Adding OpenStack-image-import-methods header to the image create
response to indicate that glance-direct Image Import method is
available.

Change-Id: Ie70abd0737e4ddf52fded941d7abc9d9d1eb285a

openstack/glance,openstack/glance,openstack/glance