Start work on 1:0.2.91.3
gpu-manager.c: remove xorg.conf if mesa is selected and binary drivers are still in xorg.conf
Release 1:0.2.91.3
Force removal of jockey on upgrades.

It has been replaced with ubuntu-drivers-common two cycles ago, removed from
trusty, and now just crashes due to API changes in aptdaemon. (LP: #1216193)
releasing package ubuntu-drivers-common version 1:0.2.91.4