Fix the lock task cts test.

This test used to rely on onPause being called as a sign that a new activity
had been launched.
But onPause may be called without a new activity being launched.

To fix this test:
The activity that is launched signals that it has been launched with a
broadcast intent.

Also: the main event that can take a long time is to destroy the activity.
So, giving a long timeout when destroying the activity, and a shorter timeout
for the rest.

BUG:17890673

Change-Id: Ieb51ee64dafe26d8633f280c6554bc8e4ebf3bad