kiosk: Fix kiosk enable not showing up regression.

When sign in screen shows up for the 2nd time, auto enrollment client already
exists and it is not started to check again. |auto_enrollment_check_done_| is
set to false would stay as false because the done callback is never going
to happen.

BUG=314166
TEST=KioskTest.KioskEnableAfter2ndSigninScreen
R=joaodasilva@chromium.org

Review URL: https://codereview.chromium.org/48993008

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@232736 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 232736
Mojo: Add a script to help with building/testing parts of Mojo.

R=darin@chromium.org, darin
NOTRY=True

Review URL: https://codereview.chromium.org/45113002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@232737 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 232737