Have HTTP-redirect fetch call main fetch with recursive=false sometimes

Otherwise a navigation wouldn't get callbacks from processing its redirect.

Closes #1629.

fetch.bs

@@ -5352,8 +5352,20 @@ run these steps:
  <li><p>Invoke <a>set <var>request</var>'s referrer policy on redirect</a> on <var>request</var> and
  <var>actualResponse</var>. [[!REFERRER]]
 
+ <li><p>Let <var>recursive</var> be true.
+
+ <li>
+  <p>If <var>request</var>'s <a for=request>redirect mode</a> is "<code>manual</code>", then:
+
+  <ol>
+   <li><p>Assert: <var>request</var>'a <a for=request>mode</a> is "<code>navigate</code>".
+
+   <li><p>Set <var>recursive</var> to false.
+  </ol>
+
  <li>
-  <p>Return the result of running <a>main fetch</a> given <var>fetchParams</var> and true.
+  <p>Return the result of running <a>main fetch</a> given <var>fetchParams</var> and
+  <var>recursive</var>.
 
   <p class=note>This has to invoke <a>main fetch</a> to get <var>request</var>'s
   <a for=request>response tainting</a> correct.