Remove deferred relaunch

It was changed from defer-destroy to defer-relaunch in commit f81c1d16.
However, it is fine to relaunch directly without waiting for being
paused. Because the client should still handle the lifecycle
sequentially and other non-pausing states also relaunch directly.

Bug: 163976519
Test: CtsWindowManagerDeviceActivity
Test: Declare a PiP activity without handling config change.
      Enter PiP from landscape to portrait.
Change-Id: Ief6fcbb853ab734c4955edc4ed065c659289a2bb