Fix issue with wanfed lan ip conflicts.
Prior to this commit, the connection pools were unaware which datacenter the
connection was associated with. This meant that any time servers with
overlapping LAN IP addresses and node shortnames existed, they would be
incorrectly co-located in the same pool. Whenever this occurred, the servers
would get stuck in an infinite loop of forwarding RPCs to themselves (rather
than the intended remote DC) until they eventually run out of memory.
Most notably, this issue can occur whenever wan federation through mesh
gateways is enabled.
This fix adds extra metadata to specify which DC the connection is associated
with in the pool.
Derek Menteer