Fix icon update race condition

When the icon is set in QSIconViewImpl there are two different paths
that could be followed:

* If the `State.state` changes (and then the tint of the icon should
  change), we animate the color of the existing icon, and only set the
  new icon when the animation is finished.
* If the `State.state` didn't change, we immediately set the new icon.

Therefore, if two calls to change the state come in short succession, it
could happen that the icon for the first call is set after the one for
the second call (because it was set at the end of an animation).

If that is the case, with this fix, we ignore the schedule icon change
at the end of the animation if another icon has been set in the
meantime.

Test: atest QSIconViewImplTest_311121830
Test: manual, turn APM on and off multiple times with QS open
Fixes: 311121830
Fixes: 293524288
Flag: None

Change-Id: Id150f36d10c374f30e72d658bd833e4eae7677b4