Fix secondary lock screen implementation such that DevicePolicyKeyguardService...

Fix secondary lock screen implementation such that DevicePolicyKeyguardService calls are made on the main (UI) thread.

For implementations of DevicePolicyKeyguardService to provide a SurfacePackage via SurfaceControlViewHost, they must be running on the UI thread.
Additionally, fix dismissal logic to bypass re-checking the secondary lockscreen, and add defensive null checks.

Bug: 136085151
Bug: 151365616
Test: atest AdminSecondaryLockScreenControllerTest
Test: atest KeyguardUpdateMonitorTest
Change-Id: Ibcd7090f50831cddbf952914adf020015750afd8