iscsi group name preserve backward compatibility

iscsi group name preserve backward compatibility

Recently we renamed the group_name for iscsi iscsigws where previously
it was named iscsi-gws. Existing deployments with a host file section
with iscsi-gws must continue to work.

This commit adds the old group name as a backoward compatility, no error
from Ansible should be expected, if the hostgroup is not found nothing
is played.

Close: https://bugzilla.redhat.com/show_bug.cgi?id=1619167
Signed-off-by: Sébastien Han <seb@redhat.com>