requested to merge ondrej-fix-timing-error-in-statistics-system-test-v9_18 into v9_18
The statistics system test makes a query to foo.info to check for the pending connections because the ans4 doesn't respond to the query.
This might or might not (depending on exact timing) increment the failed TCP connection counter when the query is retried over TCP because ans4 doesn't listen on the TCP.
Wait for the 'connection refused' in the ns3 log file to be able to count the exactly 1 failed TCP connection.
(cherry picked from commit 0227d82d)