fix: reset sapi response code (#964)

* fix: reset sapi response code
It turns out that the sapi response code is NOT reset between requests by the zend engine. This resets the code for cgi-based requests.
fixes: #960

* update response header test

* fix assertion

* appears to affect workers too

testdata/response-headers.php

@@ -7,7 +7,9 @@ return function () {
     header('Foo2: bar2');
     header('Invalid');
     header('I: ' . ($_GET['i'] ?? 'i not set'));
-    http_response_code(201);
-    
+    if ($_GET['i'] % 3) {
+        http_response_code($_GET['i'] + 100);
+    }
+
     var_export(apache_response_headers());
 };