Fix remaining jank in secure add-widget transition.

Wait for activity to launch before dismissing the keyguard.
Otherwise we see launcher/last activity waiting for the
picker to start up.

Also remove camera transition workaround obviated by:
  Iefee62061962625b622ff2cf9a307d9429c2ad54

Bug:7482560
Change-Id: I554ddffb7981488fa8a81933842b0c7730e775f3