This was testing that _check_for_iscsi was called, which is part of
evaluate_hardware_support for the in-tree hardware manager.
evaluate_hardware_support is called at hardware manager instantiation,
which can happen when dispatch_to_managers is called. The hardware
manager instances are cached, so calling dispatch_to_managers won't
always invoke _check_for_iscsi. As such, these tests were intermittently
failing.
Mock _check_for_iscsi at the class level for these tests (since it's
unrelated), and don't check that it was called.
Change-Id: Iefca50c4c231c5eafd199bf8da6649bc3008a8fa
7ab53e34b0