Revert "Apply FLAG_SHOW_WHEN_LOCKED within tasks."

This reverts commit f7ad8557.

After careful consideration this would prove to be a security leak to leave it in. Tasks could deliberately launch dialog activities that don't want to be seen in an unsecure setting. These would then be visible over the task background.

Change-Id: Ia7e984bc9616573af6c7772f6ea0f2dd588bb85d