The listening socket must be opened on the loopback interface,
otherwise the test client won't be able to connect.

Also, name resolution can take a lot of time to fail, so we must
wait longer when trying to connect to a non-existing host.

Change-Id: I6d6744bc89e6e851cf49db5ae2c19aa652c0a8a4
Reviewed-by: Liang Qi <liang.qi@theqtcompany.com>