pjax: Fix state corruption

If a new PJAX request is started before the current PJAX request finishes,
leave the user interface in a consistent state.

  * Finish and re-start the loadingbar animation
  * Ensure the overlay is hidden
  * Cancel all current animations (without using clearTimeout)

This also fixes other nuances such as the help tips not working after the
PJAX ui state was corrupted.
pjax: Release ticket when navigating away
Merge pull request #892 from greezybacon/issue/pjax-various

pjax: Various issues

Reviewed-By: Peter Rotich <peter@osticket.com>