Fix issue #17536024: The am start's wait option doesn't...

...give time in some cases

This switch to multiple stacks broke the check to determine if it
should actually wait for a new activity to be shown.  The new check
now also requires that the top activity be resumed, which means
we may get some false positives where we decide to wait and shouldn't,
but that is better than consistently not deciding to wait in some
cases when we should.  (And we will always finish waiting then next
time something becomes visible).

Also add another time, which is how long it took from the startActivity
call to return with the result.  And fix when we decide to report that
we are done so that, in the case where we are bringing an existing
activity to the foreground, we don't wait until its animation is complete.

Change-Id: Id38ca0070f04e7bf8c73e131fb055808553a0e2f