Revert "Register term_handler for all zuul apps"

This reverts commit 00d7ea51fd1633a141b2e97291baa425be1680c8. It
intended to refactor common code paths for signal handling. However in
our dockerized deployment this seems to completely break signal
handling. Thus it needs to be reverted.

Change-Id: Id5731557ff9a363c7a3d9438a8efcd476e38380c
6 files changed