Revert "Active Display: check if recievers and listeners are registered"

This reverts commit 16384847ed731e25b1a63f4fd921c9b4808ab674.
Active display: Unify (un)registering callbacks and add proper checks.

Change-Id: Ie4c4660a54d2c60831f7a3bcc66b3a9ca1d035f2