Just a couple of Stasis-HTTP nitpick fixes.

* Fixed crash when res_stasis_http is unloaded before the
  implementation modules.
* Cleaned up test initialization for test_stasis_http.so.


git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@386928 65c4cc65-6c06-0410-ace0-fbb531ad65f3