Prevent cancellation of merge polling after OTA reboot am: 542d836c5b

Original change: https://android-review.googlesource.com/c/platform/system/update_engine/+/3456206

Change-Id: I69ac15e3c2acfdc4203a00be09df269b2dc2538a
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>