typo fix in exit message
typo fix in exit message

blu3sh3ll/slowhttptest,rodrigoac/slowhttptest,drat/slowhttptest,drat/slowhttptest,erikdejonge/slowhttptest,shekyan/slowhttptest,michalkoczwara/slowhttptest,rodrigoac/slowhttptest,erikdejonge/slowhttptest,shekyan/slowhttptest,blu3sh3ll/slowhttptest,michalkoczwara/slowhttptest