Tests: fixed exclusive port numbering.

To ensure port uniqueness, listen option was added for generated TCP sockets.

http_resolver.t

diff --git a/http_resolver.t b/http_resolver.t
index 6b34931..c775552 100644
--- a/http_resolver.t
+++ b/http_resolver.t
@@ -533,7 +533,7 @@
 	my $tcp = 0;
 
 	if ($extra{tcp}) {
-		$tcp = port(3, socket => 1)->listen();
+		$tcp = port(3, socket => 1);
 		$sel->add($tcp);
 	}
 

lib/Test/Nginx.pm

diff --git a/lib/Test/Nginx.pm b/lib/Test/Nginx.pm
index da1ce50..f19bc76 100644
--- a/lib/Test/Nginx.pm
+++ b/lib/Test/Nginx.pm
@@ -323,6 +323,7 @@
 			Proto => 'tcp',
 			LocalAddr => '127.0.0.1:' . $port,
 			Reuse => 1,
+			Listen => 1,
 		) and last;
 	}