monitor: use quorum_status instead of ceph status

monitor: use quorum_status instead of ceph status

The ceph status command returns a lot of information stored in variables
and/or facts which could consume resources for nothing.
When checking the quorum status, we're only using the quorum_names
structure in the ceph status output.
To optimize this, we could use the ceph quorum_status command which contains
the same needed information.
This command returns less information.

$ ceph status -f json  | wc -c
2001
$ ceph quorum_status -f json  | wc -c
957
$ time ceph status -f json > /dev/null

real	0m0.577s
user	0m0.538s
sys	0m0.029s
$ time ceph quorum_status -f json > /dev/null

real	0m0.544s
user	0m0.527s
sys	0m0.016s

Signed-off-by: Dimitri Savineau <dsavinea@redhat.com>