Fixed #10215 -- Ensured that there is parity between enter and leave...

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.

git-svn-id: http://code.djangoproject.com/svn/django/trunk@13978 bcc190cf-cafb-0310-a4f2-bffc1f526a37