docs: fix iscsi-direct XML example

The <initiator> element is part of <source> element.
Reviewed-by: NJán Tomko <jtomko@redhat.com>
Signed-off-by: NPavel Hrdina <phrdina@redhat.com>

docs/storage.html.in

@@ -447,10 +447,10 @@
   <source>
     <host name="iscsi.example.com"/>
     <device path="iqn.2013-06.com.example:iscsi-pool"/>
+    <initiator>
+      <iqn name="iqn.2013-06.com.example:iscsi-initiator"/>
+    </initiator>
   </source>
-  <initiator>
-    <iqn name="iqn.2013-06.com.example:iscsi-initiator"/>
-  </initiator>
 &lt;/pool&gt;</pre>
 
     <h3>Valid pool format types</h3>