Prevent cancellation of merge polling after OTA reboot am: 542d836c5b am: c4a8a40723

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

Change-Id: I84b1c78291139bbbc2414beb1d924f7a31145318
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>