tests: extend qmp test with preconfig checks

Add permission checks for commands at 'preconfig' stage.

Signed-off-by: Igor Mammedov <imammedo@redhat.com>
Message-Id: <1526556524-267991-1-git-send-email-imammedo@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Eduardo Habkost <ehabkost@redhat.com>