ipa_backup: Backup the password to HTTPD priv key

https://pagure.io/freeipa/issue/7421

Reviewed-By: Christian Heimes <cheimes@redhat.com>

ipaserver/install/ipa_backup.py

@@ -365,6 +365,10 @@ class Backup(admintool.AdminTool):
             if os.path.exists(file):
                 self.files.append(file)
 
+        self.files.append(
+            paths.HTTPD_PASSWD_FILE_FMT.format(host=api.env.host)
+        )
+
         self.logs.append(paths.VAR_LOG_DIRSRV_INSTANCE_TEMPLATE % serverid)