Update image use case tests

*Updated force_a_user_to_see_my_images module
-Updated variable names for better clarity
*Updated image_discovery_of_shared_images_owned_by_user module
-Updated variable names for better clarity
-Added setup class for image creation
*Removed image_visibility_of_images_owned_by_user module
-Removed redundant test
*Updated one_to_many_image_sharing module
*Updated one_to_one_image_sharing module
*Updated remove_all_shared_images_from_user_list module
*Updated unshare_previously_shared_image module
*Updated visibility_of_images_shared_between_users module
-Updated tests due to behavior, fixture and config changes
-Updated test steps

Change-Id: I323f4def3002d5b727497c588b246697868dcde3
Merge "Update image use case tests"