Make getCurrentController async friendly.

Ensure that getCurrentController does not have a return type. If the
view controller is cached, then the callback will be immediately called,
otherwise, we inflate the view on a bg thread.

Fixes: 276924513
Fixes: 277039068
Test: simpin, simpuk, pin, password, pattern views.
Test: no security method
Test: atest android.security.identity.cts.UserAuthTest
Test: unit tests
Change-Id: I85e60cfc6fd5a71eb00a44405620ac650867b481