Notify the TrustAgent when the token is activated.

Previously, the agent will have to query the TrustManager to see if a
recently added escrow token has been activated.  If the agent asked too
soon about the token state, then the result could be inactive.  That
will be hard to distinguish from when the token is actually inactive
because activation failed.

This change pipes the call from LockSettings to the TrustAgentService
through the TrustManager when the token is activated.  So, the trust
agent doesn't have to query, it just gets notified.

Bug: 124312230
Test: Observe the onTokenStateReceived() callback received on the trust
agent.

Change-Id: I0ac674219fd7925ba36f50bb695c9998c18226f7