Several tests referred to specific server ports even when the test
didn't actually use that server or specify that it's needed. In such
cases, the test harness substitutes the text "[not running]" as the port
number which causes many such tests to fail due to the inability to
parse the URL.  These tests are changed to use %NOLISTENPORT which will
always be substituted correctly.

When the progress callback is called during the TCP connection, an error
return would accidentally not abort the operation as intended but would
instead be counted as a failure to connect to that particular IP and
libcurl would just continue to try the next. I made singleipconnect()
and trynextip() return CURLcode properly.

Added bonus: it corrected the error code for bad --interface usages,
like tested in test 1084 and test 1085.

Reported by: Adam Light
Bug: http://curl.haxx.se/mail/lib-2010-08/0105.html

tests on machines that have broken DNS configurations (such as
those configured to use OpenDNS).

use the startup of the IPv6 test server as a substitute check for this).