Fixed issue with IME window not been added to its window token

This looks like a coding error that has always existed. The window
was added to the display window list, but not to its window token.
The issue was exposed by the switch to using the window container
hierarchy since the window was not a child of the token it wasn't
showing up in the hierarchy.

Test: Run 'adb shell dumpsys window containers' and make use the
InputMethod window shows up in the print-out.

Change-Id: I43cb5d6b3f266c1be54dd27def4c13e1ef98a4fa