net: Clarify early exit condition

net: Clarify early exit condition

On first glance, the loop in qmp_query_rx_filter() has early return
paths that could leak any allocation of filter_list from a previous
iteration.  But on closer inspection, it is obvious that all of the
early exits are guarded by has_name, and that the bulk of the loop
body can be executed at most once if the user is filtering by name,
thus, any early exit coincides with an empty list.  Add asserts to
make this obvious.

Signed-off-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Markus Armbruster <armbru@redhat.com>
Message-Id: <20210113221013.390592-2-eblake@redhat.com>
Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Signed-off-by: Markus Armbruster <armbru@redhat.com>