Play no-op-during-display-change transition immediately

Instead of just setting ready, use playNow so that we also
immediately start and send the transition to shell. Otherwise
it's possible for the system to not check if it is finished
or for changes to end-up in the "no-op" transition.

Bug: 413001499
Test: Cts tests no-longer flaking
Flag: EXEMPT bugfix
Change-Id: I3e3aa997e7628ceac7e83ac6ab0f7d21c8d43851