TPAC: Avoid 500 errs on record page due to ipv6 ignorance

TPAC: Avoid 500 errs on record page due to ipv6 ignorance

Net::HTTP does not handle ipv6 addresses properly, and is subject to
failing to return a request object if handed one (some systems seem to
prefer ipv6). This commit checks the value of the request object before
invoking any methods on it, and also short-circuits the AC lookup loop
if the host could not be resolved to avoid flooding the logs with
multiple "Unable to connect..." warnings.

If Net::HTTP grows ipv6 support, this commit can still stay in place and
the lookups will just start magically working.

Signed-off-by: Dan Scott <dscott@laurentian.ca>