CTS checks to make sure that the _contexts files on a device have
a superset of the AOSP entries.  This was removed due to concurrent
master and DR development.  Restore the entry to allow CTS to pass.

Bug: 38241921
Bug: 62348859
Test: Policy builds and is identical to oc-dev for prop ctxts.
Change-Id: I87ccbee7aadee57b8e46ede73280810362b618c0