osd: set objecter.osdmap when starts

osd: set objecter.osdmap when starts

if any OSD is full or the pause flag is set in cluster, objecter will
always try to subscribe the next osdmap using the mon client shared with
OSD. but if the OSD's osdmap is very far behind on osd maps due to some
reasons, `MonClient::sub_want_increment()` will reject the subscribe
request from OSD, because it's asking for older maps while the mon client
is about to send the request from objecter for the *next* osdmap.

so we need to update objecter with the latest local osdmap, so it is
able to skip the new osdmaps if OSD needs to catch up with the cluster
first.

Fixes: http://tracker.ceph.com/issues/17023
Signed-off-by: Kefu Chai <kchai@redhat.com>