Added a regression test for r14781. Also fixed a bug where connection.vendor...

Added a regression test for r14781.  Also fixed a bug where connection.vendor was effectively always 'unknown', causing all vendor-specific tests to be skipped.

git-svn-id: http://code.djangoproject.com/svn/django/trunk@14783 bcc190cf-cafb-0310-a4f2-bffc1f526a37