[1.2.X] Fixed #7616 -- Added advice on unix socket permissions and umasks to...

[1.2.X] Fixed #7616 -- Added advice on unix socket permissions and umasks to fastcgi deployment documentation. Thanks to Malcolm Tredinnick for the report and advice, and PaulM and cramm for reviewing the patch.

Backport of [14276] from trunk.

git-svn-id: http://code.djangoproject.com/svn/django/branches/releases/1.2.X@14277 bcc190cf-cafb-0310-a4f2-bffc1f526a37