Fix the resolvers RTT-ranged responses statistics counters

Fix the resolvers RTT-ranged responses statistics counters

When a response times out the fctx_cancelquery() function
incorrectly calculates it in the 'dns_resstatscounter_queryrtt5'
counter (i.e. >=1600 ms). To avoid this, the rctx_timedout()
function should make sure that 'rctx->finish' is NULL. And in order
to adjust the RTT values for the timed out server, 'rctx->no_response'
should be true. Update the rctx_timedout() function to make those
changes.