MDL-43440 unit tests Use correct cm identifier in unit tests
MDL-43440 unit testing: Use cmid in unit tests when it should be used.

instance is has been used instead of cmid.  This works as all id's are 1
in most cases, but not always.

accesslib_clear_all_caches_for_unit_testing was updated to clear the
$USER->access cache which would fail test when the wrong user's data was used.