ceph: only send metrics when the MDS rank is ready

When the MDS rank is in clientreplay state, the metrics requests
will be discarded directly. Also, when there are a lot of known
client requests to recover from, the metrics requests will slow
down the MDS rank from getting to the active state sooner.

With this patch, we will send the metrics requests only when the
MDS rank is in active state.

Link: https://tracker.ceph.com/issues/61524


Signed-off-by: Xiubo Li <xiubli@redhat.com>
Reviewed-by: Milind Changire <mchangir@redhat.com>
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>