mgr/ServiceMap: adjust 'ceph -s' summary

mgr/ServiceMap: adjust 'ceph -s' summary

- Do not list individual daemon ids as this won't scale for larger
  clusters
- Do not contemplate multile daemons of the same type that register with
  different "daemon_type" -- not until we actually have any that do that.
- Present counts by various groupings: distinct hosts and rgw zones to
  start.

  services:
    mon:           1 daemons, quorum a (age 4m)
    mgr:           x(active, since 3m)
    osd:           1 osds: 1 up (since 3m), 1 in (since 3m)
    cephfs-mirror: 1 daemon active (1 hosts)
    rbd-mirror:    2 daemons active (1 hosts)
    rgw:           2 daemons active (1 hosts, 1 zones)

Signed-off-by: Sage Weil <sage@newdream.net>
(cherry picked from commit ab0d8f2ae9f551e15a4c7bacbf69161e91263785)