Fix timeout notification when ping returns redirect response

Fix #728.

This fixes the issue where the call to `getResponseHeader` was causing a JS error and preventing the timeout notification from popping up. I am still unclear what was causing the problem in `getResponseHeader` since all I saw in the console was a generic `undefined is not a function` type error and then a partial stack trace into jquery code.

Signed-off-by: Don Naegely <naegelyd@gmail.com>