Dialyzer fixes in cowboy_clock
Dialyzer fixes in cowboy_clock

This is what I get for merging blindly!

Reimerei/cowboy,turtleDeng/cowboy,hairyhum/cowboy,dangjun625/cowboy,imdeps/cowboy,K2InformaticsGmbH/cowboy,bobos/ecweb,yangchengjian/cowboy,CrankWheel/cowboy,omusico/cowboy,acrispin/cowboy,rabbitmq/cowboy,276361270/cowboy,noname007/cowboy,odo/cowboy,ninenines/cowboy,nviennot/cowboy,binarin/cowboy,binarin/cowboy,yangchengjian/cowboy,bsmr-erlang/cowboy,kivra/cowboy,pap/cowboy