Update get create import tasks tests

*Updated create_import_task test
-Updated tests due to behavior, fixture and config changes
-Updated test steps
-Removed duplicate code
-Added create_multiple_simultaneous_import_tasks test
-Updated variable names
-Updated validation
*Updated get_task test
-Updated tests due to behavior, fixture and config changes
-Updated test steps
-Added get_import_task_with_metadata test
-Removed redundant get_import_task_with_metadata test
*Updated get_tasks test
-Updated tests due to behavior, fixture and config changes

Change-Id: Iee8882da606d73bd36ca761d64032b4c6f5efa20
Merge "Update get create import tasks tests"