Add get image members and get images tests

*Updated get image members module to reflect cloud cafe changes
*Updated get images module to reflect cloud cafe changes
*Updated modules aesthetic consistency
*Removed happy_path from test names
*Updated pagination test to use images created within setup class
*All get_images_by_* tests removed and submitted in this PR:
 https://review.openstack.org/#/c/58049/
*All get_images_by_<property>_sort_key tests removed and submitted in this PR:
 https://review.openstack.org/#/c/58050/
*All negative get_image_members tests removed and submitted in this PR:
 https://review.openstack.org/#/c/58046/

Change-Id: Idf6c2f7775fa179127cadb5b54e9352508ad6b6d
Merge "Add get image members and get images tests"