tests(balancer) make sure http_server always times out
tests(balancer) make sure http_server always times out

Active healthchecks produce a constant flow of requests to the
server, causing it to never timeout (in case of failed tests
where the number of requests received does not match the
list of requests expected). This turns the `timeout` argument
into a hard limit for the execution time of the `http_server`
itself.

Kong/kong,Kong/kong,Kong/kong,Mashape/kong