osd: update primary's notion of peer last_update on activate
osd: update primary's notion of peer last_update on activate

We are pushing the peer the log to bring it up to date, so
update our peer_info[peer].last_update to match.  Otherwise,
we get confused if we get, say, stray content and peer() is
called later, and we have out of date peer stats.

ajnelson/ceph,ajnelson/ceph,ajnelson/ceph,ajnelson/ceph,ajnelson/ceph,ajnelson/ceph