Fix TrustAgent showing unclear string.

TrustAgents currently show the string "Device was locked manually" if
the trustagent times out, or if lockUser() was called. Changed to show a
more generic string, informing the user that they need to authenticate
with whatever credentials they have set up (instead of using the
trustagent).

Test: LockPatternUtilsTest. Manual test lockUser and trust timeout, verify biometrics works and string appears.
Bug: 243710694
Change-Id: Ia2f3c560ad0f959f0117f8967f556c3c026747a3