Fix a timing issue in unlock signal propagation in AppSearch

There is a tiny gap between user unlock and when the unlock event
reaches AppSearch. The fact that unlock event haven't reach AppSearch
isn't suffice to say user is not unlocked. This CL added the logic to
check with UM when cache misses.

Bug: 151359749
Test: manual
Change-Id: I49f0754d53fc4d391245917bb35b726a305e4e30