[1.2.X] Fixed #11193 -- WSGI handler not properly handling lock on error in...

[1.2.X] Fixed #11193 -- WSGI handler not properly handling lock on error in load_middleware. Thanks to Phillip Sitbon.

Backport of [15205] from trunk

git-svn-id: http://code.djangoproject.com/svn/django/branches/releases/1.2.X@15206 bcc190cf-cafb-0310-a4f2-bffc1f526a37