Re-adding the task to recents once task affinity updated

Task affinity was relinquished to another activity after the
task added to recent tasks, so there was nothing to trim when
the new task being added. Therefore, it ended up with many
duplicated recent tasks.

Bug: 223555529
Test: repeatedly setting wallpaper
Change-Id: Ib221daa4487c6000bdbf8c0cb0515d3132aacb95