Unregister listeners when settings disabled or connect to wifi

Without this change, even when user disabled the mobile data/auto data switch feature, or when connect to wifi, we're still listening and processing the signal strength/service state/display info events, which unnecessary comsumes power.

Fix: 389591869
Test: QA verified all auto data switch test cases b/409423653
Flag: EXEMPT bugfix
Change-Id: I392c059727c425d17b0a51808db894553ce580c3