toaster: work around 'database is locked' error

toaster: work around 'database is locked' error

When sqlite can not cope with a stream of 'insert' queries it throws
'database is locked' exception.

Wrapping model.save in transaction.atomic context and repeating the call
should solve this issue.

Signed-off-by: Ed Bartosh <ed.bartosh@linux.intel.com>
Signed-off-by: brian avery <avery.brian@gmail.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>