Fix device not rebooting after watchdog triggered staged rollback

RollbackPackageHealthObserver doesn't log to statsd for non mainline
rollbacks. There was a bug where we skipped rebooting after a rollback
for non-mainline modules in RollbackPackageHealthObserver.

Test: atest RollbackTest
Bug: 129335707
Change-Id: I9e35c87a16b96eef61dbd1d92da7fb8bd808f908