pveceph: create mgr with mon, use nodename for id

pveceph: create mgr with mon, use nodename for id

we now want to add a ceph-mgr daemon to every node where a ceph-mon
daemon runs, as per ceph documentation recommendation, because in
luminous the mgr daemons will not be automatically created/started
with a monitor anymore

we also give the createmon an optional id parameter, so that one
can set a custom id, and make the creation/removal of the manager
optional but the default

Signed-off-by: Dominik Csapak <d.csapak@proxmox.com>