Display grant trust messages on the lock screen

Before, nothing was registered for the trust
granted message callback and we were always showing
the default trust granted message.

Test: locally/manually add FLAG_DISPLAY_GRANT_TRUST_MESSAGE
to all messages in TrustAgentWrapper. Observe messages
are shown on the lock screen.
Test: atest KeyguardIndicationControlerTest
Fixes: 213911325

Change-Id: I239b71dcd14d7edde7d99a54cfbee43a211badc2