toasterui: do not use transactions if the database autocommits

toasterui: do not use transactions if the database autocommits

Some databases, notably the SQLite3 adapter, force autocommits even if
the autocommit is turned off. The behavious is tracked in this bug:
http://bugs.python.org/issue8145#msg109965

Django refuses to work with autocommit off in this case, so we have
to take the same precautions when using manual transaction support.

[YOCTO #7363]
[YOCTO #7365]

Signed-off-by: Alexandru DAMIAN <alexandru.damian@intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>