Further images test fixes

*Updated create_export_task_negative module
-Removed skip tags
-Fix broken test
-Removed test tag
*Updated delete_image_negative module
-Fixed broken test due to improper method used
*Updated get_image_file module
-Updated skip tags
-Fixed broken test due to improper method used
*Updated update_image module
-Fixed broken test due to improper method used
*Updated update_image_negative module
-Fixed broken tests due to improper method used
-Updated test steps
-Moved image creation to setup class
-Removed unnecessary code

Change-Id: Ib9a2f50fe41cab5661e573b5436c8d81d27c3891
Merge "Further images test fixes"