Add integration tests for the CLI chgrp plugin
Add image to the list of objects to test and use it as default
Add integration tests for fileset chgrp using CLI

- Test /Fileset:id changes the group of the fileset
- Test /Image:id does not move the fileset
Add test for chgrp with non-admin user not member of new group
Divide CLI test abstract class into root and non-root classes
Add failing test for chgrp to a non-member group
Fix flake8 warnings
Simplify chgrp test suite by returning objects and using query.get()
Fix input group check and add integration tests for invalid group input
Fix group check logic in chgrp CLI command
Check session owner is member of the target group in CLI chgrp

- Update corresponding integration tests to except NonZeroReturnCode
Parametrize testObject() using multiple decorators
Merge pull request #1751 from sbesson/10968_chgrp

CLI integration tests: chgrp plugin