iscsi-gw: move repository configuration to ceph-iscsi-gw
iscsi-gw: move repository configuration to ceph-iscsi-gw

This is something that has nothing to do in `ceph-common`, this
is too specific to `ceph-iscsi-gw` role.

Signed-off-by: Guillaume Abrioux <30a9df5a0293a6108675377fa1673f7aa713f915@redhat.com>

ceph/ansible-ceph-common