POST v2.0/images/{image_id}/members - Refactoring

Refactors all tests to use images_behavior functionality.

Change-Id: I6532ad54c23d74c8501c5adfae79a549590d417c
PUT v2.0/images/{image_id}/members/{member_id} - Refactoring

Refactors all tests to use images_behavior functionality.

Change-Id: I6cde7cba34959db251d965a92be94b6a2b3611d4
Merge "PUT v2.0/images/{image_id}/members/{member_id} - Refactoring"
Merge "POST v2.0/images/{image_id}/members - Refactoring"