Cancel the existing recents animation before any initialization

- In the rare case that we are canceling the recents animation as a
  part of starting another recents animation, ensure that we do it
  before we move the target activity to be visible, otherwise the
  cancelation will undo the previous work.

Bug: 193851085
Test: atest RecentsAnimationControllerTest
Change-Id: I22589a034eab3b1fab10f4b677f777b282305bbd