[1.2.X] Fixed some Oracle backend test DB creation code bugs.

Made saving of modified settings compatible with multi-db, removed dead and superfluous code.

Backport of [14489] from trunk

git-svn-id: http://code.djangoproject.com/svn/django/branches/releases/1.2.X@14490 bcc190cf-cafb-0310-a4f2-bffc1f526a37