Fixing issue with wrong initial multi-window mode.

- When an activity is started into a new task in the adjacent stack, we
  need to initialize the multi-window mode in order to ensure that the
  app gets the required callbacks when it leaves multi-window mode. This
  flow doesn't go through the normal mechanism to schedule changes to the
  app, so we just initialize it manually.

Bug: 38028679
Test: android.server.cts.ActivityManagerDockedStackTests
Test: #testLaunchToSideMultiWindowCallbacks
Change-Id: I783d03bbb3f7e197dca2f8411e23edb7680a9a86