dashboard: add ceph iscsi management

dashboard: add ceph iscsi management

When deploying with ceph-iscsi nodes and dashboard enabled, we need to
add the ceph iscsi gateway endpoints to the dashboard configuration and
add the mgr ip address in the trusted list in the iscsi gateway
configuration file.

Closes: #4638
Closes: https://bugzilla.redhat.com/show_bug.cgi?id=1764173
https://docs.ceph.com/docs/master/mgr/dashboard/#enabling-iscsi-management

Signed-off-by: Dimitri Savineau <dsavinea@redhat.com>
(cherry picked from commit d050391cbbe8a56d1cf44e744a02e4aa3f0583e5)