setup content observer statically

Instead of waiting for the first time we get the app op default mode,
just register the content observer for the sms & call log restriction.
This is temporary code anyway and will be removed according to a
STOPSHIP comment. So, the minor hit taken during system start is okay
for now.

Test: Device boots.
Change-Id: I55cc57ddfe80acf304b5126db16f5813a97c7042
Fixes: 119080532