Add create export task tests

*Added create_export_task module:
-Added create_export_task test
-Updated variable names for clarity
-Updated test steps
-Updated placement of error validation
*Added create_export_task_negative module:
-Added attempt_duplicate_export_task test
-Added export_coalesced_snapshot test
-Updated test steps
-Updated module name
*Added create_export_task_positive module:
-Added export_same_image_two_different_containers test
-Updated test steps
-Updated module name
-Updated for loop

Change-Id: I899b1740477bc6fbda1ad9f62b063357c9319bad
Update store image file tests

*Removed upload_image_file module
-Updated and moved tests to store_image_file module
*Removed upload_image_file_negative
-Updated and moved tests to store_image_file_negative module
*Updated store_image_file module
-Updated method call
-Updated image to be validated
-Moved and updated immage creations to setup class
*Added store_image_file_negative module
-Removed unnecessary code
-Moved image creations to setup class

Change-Id: I8cb20c4c15493487876c7b23649e2235e6e1ae4f
Merge "Add create export task tests"
Merge "Update store image file tests"