Remove race conditions in comment voting.
Remove race conditions in comment voting.

@Xyene please review.

monouno/site,Minkov/site,monouno/site,Minkov/site,Minkov/site,monouno/site,monouno/site,DMOJ/site,DMOJ/site,DMOJ/site,Minkov/site,DMOJ/site,monouno/site