Try alternate addresses more agressively.

Attempt to connect to alternate addresses if the connect doesn't
succeed in 180ms, and cut wait time between connection attempts
in half for each additional, if no connection was established.

Take the first connection to succeed and close the others.

This makes whois more responsive when e.g. IPv6 service took long
time or fail to respond.

PR: 158125
Submitted by: Mark Andrews <marka isc org> (with changes from me)
MFC after: 2 weeks