Use https rather than http when querying for open Trac tickets when running unit tests

Querying the HTTP version was causing a redirect, which in turn was mangling
the query params and forcing Trac to return an empty CSV. As a result, all
tickets were being registered as closed, causing all tests to run.

This fix ensures that tests marked @ticket with the number of a closed ticket
will not be run (unless the force-known-bugs flag is flipped)

Fixes #5876

git-svn-id: https://buddypress.svn.wordpress.org/trunk@9022 cdf35c40-ae34-48e0-9cc9-0c9da1808c22