SupervisedUsers : Fix transaction cleanup
When we create SU, it is a multi-step process. If creation fails on a late stage, we need to undo changes made on earlier stages (like adding user to a list, and creating home directory).
At some point this clean-up process got broken.
This CL fixes that.


BUG=313039
R=nkostylev@chromium.org

Review URL: https://codereview.chromium.org/63173012

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@235134 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 235134