Dismiss keyguard when target user has no password

Only lock on starting user switch if target user has
a secure keyguard. Current user might be currently
locked or unlocked.

Likewise, before completing user switch, dismiss
keyguard if target user doesn't have a secure keyguard.

Bug: 199862745
Test: atest UserControllerTest

Change-Id: I77bd58c64f20e4cdc8d37f57168d3a47c903ded4