retry basic auth also when IAM returns 400

roles/pep/templates/pep.js.j2

@@ -158,7 +158,7 @@ function requestToken(context){
         context.authn.verified_token =
           JSON.parse(Buffer.from(context.authn.token.split('.')[1], 'base64url').toString())
         return context
-      } else if (reply.status === 401){
+      } else if (reply.status === 400 || reply.status === 401){
         var options = {
           "body" : "grant_type=password&username="+context.authn.user+"&password="+context.authn.password
         }