Browser enrollment succeeds once the device is ACTIVE, but the
macOS URL handler failed whenever install re-bootstrapped a tray
LaunchAgent the PKG had already installed. Skip registration when
the plist is current, treat live bootstrap as best-effort, and
exit successfully if the device is already enrolled so retries
do not show "Enrollment failed".
Signed-off-by: Ludovic Vielle <ludovic@probo.com>