SSL support directories not being cleaned up

[nirvdrum]

It looks like BrowserMob Proxy isn't cleaning up the SSL support directories when a proxy is shutdown. This has resulted in me exhausting inodes several times over the past few weeks. I've tracked the problem down to one line that seems to have been intentionally inserted and I don't know the history around that. I'll submit a pull request and maybe someone can weigh in.

[lightbody]

Leaving this ticket open, but see my comment in #109 for why I couldn't accept that pull request.