msg/Connection: protect peer_addrs with safe_item_history<>

msg/Connection: protect peer_addrs with safe_item_history<>

The peer_addrs can be updated during the initial connection handshake,
but we don't want users (e.g., dout()) to race with an update and
wander off into bad memory.

We use the same strategy for Messenger's my_addrs.

Fixes: http://tracker.ceph.com/issues/37807
Signed-off-by: Sage Weil <sage@redhat.com>