Merge "Remove nullability of executorService" into main am: 61741bfa9f

Original change: https://android-review.googlesource.com/c/platform/packages/modules/Virtualization/+/3541279

Change-Id: I30e6f4d1b3d82197cdc6c8d8dea4455b247952c1
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>