Prevent an infinite loop in get_recent_address().

Prevent an infinite loop in get_recent_address().

When a node is offline, but we still have edges to it that have the same
address as we already have in our address cache, an infinite loop would
happen in get_recent_address(), because we forgot to advance the pointer
in the list of known addresses, and kept looking at the same one over
and over.

Thanks to Sven-Haegar Koch for spotting the bug and providing
diagnostics.