Updated Redis-server installed from wheezy-backports 

@alonswartz

Addresses turnkeylinux/tracker/issues/143

I was hoping to also address turnkeylinux/tracker/issues/158 but as per my comment on the issue, it seems that the `/var/www/canvas/tmp` directory is already set to be owned by `www-data` so not sure why it doesn't work OOTB. See here: https://github.com/turnkeylinux-apps/canvas/blob/master/conf.d/52canvas-configs#L69