fix: restore autoPrefix property of Href (sabre-io#1514)

use of this property in code was removed in PR
sabre-io#801
But the property is left here because old data may still exist
that has this property saved.

See discussion in sabre-io/Baikal#1154

lib/DAV/Xml/Property/Href.php

@@ -34,6 +34,19 @@ class Href implements Element, HtmlOutput
      */
     protected $hrefs;
 
+    /**
+     * Automatically prefix the url with the server base directory.
+     * Note: use of this property in code was removed in PR:
+     * https://github.com/sabre-io/dav/pull/801
+     * But the property is left here because old data may still exist
+     * that has this property saved.
+     * See discussion in issue:
+     * https://github.com/sabre-io/Baikal/issues/1154.
+     *
+     * @var bool
+     */
+    protected $autoPrefix = true;
+
     /**
      * Constructor.
      *