adb: check the current Settings values after adding ContentObserver

ContentObserver is edge sensitive, once we add it,
we should also check the current values, if the
things we are looking for are already enabled.

Bug: 402444824
Test: v2/al-eng/al_dts_hw_postsubmit
Flag: EXEMPT cleanup
Change-Id: I1e965a7f80377320ca60605b9675a0c8414d8e62
Signed-off-by: Roman Kiryanov <rkir@google.com>