Merge "[WM] Don't moveTaskToBackInner if it's already detached" into main am: d17e9435e5 am: 6fa6c1627f

Original change: https://android-review.googlesource.com/c/platform/frameworks/base/+/3304112

Change-Id: I85cf1b736766e8ce9ace4d53958af389dab79aa5
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>