Change the standalone sumstats mode to work incrementally.
Now the standalone sumstats works even if Bro is shutting down by blocking.
Merge remote-tracking branch 'origin/topic/seth/sumstats-standalone-fix'

* origin/topic/seth/sumstats-standalone-fix:
  Now the standalone sumstats works even if Bro is shutting down by blocking.
  Change the standalone sumstats mode to work incrementally.