Coverage: Don't attempt to set cookie domain when it is "localhost" (#…

…6210)

See https://stackoverflow.com/questions/1134290/cookies-on-localhost-with-explicit-domain

src/Codeception/Coverage/Subscriber/LocalServer.php

@@ -201,8 +201,13 @@ protected function startCoverageCollection($testName)
             // we need to separate coverage cookies by host; we can't separate cookies by port.
             $cookieDomain = isset($c3Url['host']) ? $c3Url['host'] : 'localhost';
         }
+
+        $cookieParams = [];
+        if ($cookieDomain !== 'localhost') {
+            $cookieParams['domain'] = $cookieDomain;
+        }
 
-        $this->module->setCookie(self::COVERAGE_COOKIE, $value, ['domain' => $cookieDomain]);
+        $this->module->setCookie(self::COVERAGE_COOKIE, $value, $cookieParams);
 
         // putting in configuration ensures the cookie is used for all sessions of a MultiSession test