[maven-release-plugin] prepare release v2.6.0
[maven-release-plugin] prepare for next development iteration
Change unrouteable address for testConnectTimeout

Some networks actually try to route the unroutable private IP address that
was being used by testConnectTimeout (172.31.255.1), and then report a
connection refused instead of a timeout, causing the test to fail.

Instead switch to the address 240.0.0.1, which is reserved for future use
and is routable, but is effectively a black hole.