CallHTTP should be able to set more LWP::UserAgent options

[Galen Charlton]

It would be handy if the CallHTTP A/T reactor (introduced in bug 1860703) could set additional parameters to its LWP::UserAgent object.

At minimum, being able to set 'timeout' to a value other than the default of 180 seconds would be good, as an endpoint that is down could otherwise tie up open-ils.action_trigger backends very quickly.

'ssl_opts' would be another good one to be able to manipulate, both to relax and strengthen SSL options.

Some environments might also need to set 'proxy'.