[tests] force POSIX::WNOHANG() autovivification (fixes #3110)

x-ref:
  "RPM build fails at Lighttest.pm"
  https://redmine.lighttpd.net/issues/3110

tests/LightyTest.pm

@@ -137,7 +137,7 @@ sub wait_for_port_with_proc {
 
 		# the process is gone, we failed
 		require POSIX;
-		if (0 != waitpid($child, POSIX::WNOHANG)) {
+		if (0 != waitpid($child, POSIX::WNOHANG())) {
 			return -1;
 		}
 		if (0 >= $timeout) {