Don't start work challenge unless auto-cancel.

This bit of logic ensures that the notification from a work app
doesn't get cancelled prematurely when the user taps on it and then
dismisses the work challenge window.
If an activity is started for a locked profile user, work challenge
will be started by the ActivityStartInterceptor logic anyway, so
this logic doesn't add much value if the notification doesn't auto
cancel on click.

This CL allows intents leading to showWhenLocked activities to be
invoked by tapping on a notification, like an incoming call
notification from the dialer.

Bug: 279147687
Test: manual with incoming call
Change-Id: I2e5f3bfab31e3ebc1d1e2713f86570ff5ee0420a