run_bisect still installed to the wrong location, making the debbisect tool useless

There was some back-and-forth with the run_bisect scripts in the commit history but even the latest commits do not fix the situation. Right now, run_bisect and run_bisect_qemu are installed as /usr/share/devscripts/scripts and not in a directory called like that because it's never created. This means that devscripts in Debian right now ships a broken debbisect tool. The first commit in this merge request fixes this by creating the scripts directory.

This merge request also contains two other commits that improve the HTTP proxy of debbisect which you may or may not want to include as well. But even if you do not include those two additional commits because of the freeze, the debbisect tool is not completely useless even without them.