Added content connect timeout

Added content connect timeout

Make tpac server-side added content lookups exit after a brief timeout
when the apache module is unable to open a connection to its own
top-level hostname (the virtualhost, apache->hostname).

As noted in the code comments, even though we are using Net::Server::NB
(non-blocking), it's only non-blocking in the sense of content
retrieval, not in how it calls connect() under the covers.

Signed-off-by: Bill Erickson <berick@esilibrary.com>