osd/PeeringState: renew before activate messages; send after activated

osd/PeeringState: renew before activate messages; send after activated

We want to renew before we prepeare or send activate messages so that we
have the opportunity to include leases in them (coming soon!).

And we do not want to send explicit lease messages until we know that the
peers have activate.  In particular, we want to avoid queueing a notify
(via pending_activators) and then sending a lease that will arrive before
it.

Signed-off-by: Sage Weil <sage@redhat.com>