Better logging for Device Policy Changes in trust

Only log DevicePolicyChanged if it actually changes in a way that
affects trust. Log when lockUser is called with what Trustagent called
it.

FLAG: EXEMPT logging change
BUG=426276010
Test: manually running Extend Unlock & Device Policy workflows
Change-Id: I287f07b354948d38e2c99c2506450b661899b588