Ignore var-naming[pattern] to foreign role vars

[cavcrosby]

Fixes #4095.

When working on this issue, I ran into another bug when writing a test case to test my solution to the issue. The bug I ran into was when running a test case that would lint a playbook from ./examples/playbooks that contained a include_role/import_role task with a FQCN role as its argument. I noticed that the test case would pick up violations from other lintables that I didn't specify as an argument to my runner instance. I suspect this is because _rolepath currently doesn't handle FQCNs, which results in the basedir being returned and can cause _look_for_role_files to return additional unexpected files. This can be seen when running pytest test/test_utils.py::test_find_children_in_playbook from another fork branch I made to showcase this https://github.com/cavcrosby/ansible-lint/tree/ignore-foreign-role-vars-revert-utils. The changes to fix said bug are consolidated into utils.py.

To add, said bug probably won't affect an end user unless they purposefully contain violations in their Ansible yaml like in the case of ansible-lint. That said, I would think we would want to address this for development purposes.