Setting ADB_ENABLED may result in a SecurityException.

If the restriction UserManager.DISALLOW_DEBUGGING_FEATURES is enforced,
then any attempt to set ADB_ENABLED will result in a SecurityException.
This can result in the device not being able to boot.
Bug: 18433477

Change-Id: I21e4b406ad0fa89b7d4b678eac1baf212a3c7acd