Storage nodes undergoing Graceful Exit have up to now been receiving
hostnames for all other storage nodes they need to contact when
transferring pieces. This adds up to a lot of DNS lookups, which
apparently overwhelm some home routers. There does not seem to be any
need for us to send hostnames for graceful exit as opposed to IP
addresses; we already use IP addresses (as given by the last_ip_port
column in the nodes table) for all the GET and PUT orders we send out.
This change causes IP addresses to be used instead.
I started trying to construct a test to ensure that the behavior
changed, but it was rabbit-holing, so I've begun to feel that maybe this
change doesn't require one; it is a very simple change, and very much of
the same nature as what we already do for IPs in CreateGetOrderLimits
and CreatePutOrderLimits (and others).
Change-Id: Ib2b5ffe7a9310e9cdbe7464450cc7c934fa229a1
8616fc146d