tests: split mtap0 cleanup into two apply calls

nmstate rejects deleting mtap0 as mac-vlan when it currently exists
as mac-vtap. Split the cleanup into two separate libnmstate.apply
calls: first deletes mtap0 as mac-vtap (matching the actual type),
then a second call cleans up any leftover mac-vlan profile with the
same name.

Without this fix, mtap0 stays on eth1 after test_macvtap_parent_ref_by_mac,
blocking macvlan/macvtap passthru and macsec tests that follow.

Signed-off-by: Vladimír Beneš <vbenes@redhat.com>