[1.2.X] Fixed #10215 -- Ensured that there is parity between enter and leave...

[1.2.X] Fixed #10215 -- Ensured that there is parity between enter and leave transaction calls in loaddata when commit=False. The test case for this is the fixtures_regress unittests under MyISAM, which were failing previous to this fix. Thanks to MockSoul for the report.

Backport of r13978 from trunk.

git-svn-id: http://code.djangoproject.com/svn/django/branches/releases/1.2.X@13979 bcc190cf-cafb-0310-a4f2-bffc1f526a37