toaster: Update API used to make runbuilds methods run in transactions

toaster: Update API used to make runbuilds methods run in transactions

runbuilds previously had its methods decorated with
transaction.commit_on_success, which is now deprecated. transaction.atomic
is an (almost) drop-in replacement for this, so use this instead.

[YOCTO #8364]

Signed-off-by: Elliot Smith <elliot.smith@intel.com>
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>