iotests/mirror-top-perms: Adjust imports

iotests/mirror-top-perms: Adjust imports

We need to import subpackages from the qemu namespace package; importing
the namespace package alone doesn't bring the subpackages with it --
unless someone else (like iotests.py) imports them too.

Adjust the imports.

Signed-off-by: John Snow <jsnow@redhat.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Reviewed-by: Hanna Reitz <hreitz@redhat.com>
Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Reviewed-by: Kevin Wolf <kwolf@redhat.com>
Message-Id: <20210923180715.4168522-5-jsnow@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>