The glance client will be deprecated one day. Projects using it should
switch to using the OpenStack SDK instead.
Also add "attrs" to requirements.txt. It was previously pulled through
python-glanceclient.
Change-Id: I35c598d318348c2b14323ea29c8347312733f8bc
Signed-off-by: Cyril Roelandt <cyril@redhat.com>