mgr, mon: allow normal ceph services to register with manager

mgr, mon: allow normal ceph services to register with manager

Additionally, introduce `task status` field in manager report
messages to forward status of executing tasks in daemons (e.g.,
status of executing scrubs in ceph metadata servers).

`task status` makes its way upto service map which is then used
to display the relevant information in ceph status.

Signed-off-by: Venky Shankar <vshankar@redhat.com>
(cherry picked from commit 5c25a018643b10aa78db8270cae1476f71d8f4f4)

 Conflicts:
	src/messages/MMgrReport.h
	src/mgr/DaemonServer.cc
	src/mgr/ServiceMap.h