mysql-apt-config takes a verry long time to install on Ubuntu 14.04.1
I suffered with the same problem and I found the solution at the link that you mentioned:
export DEBIAN_FRONTEND=noninteractive
echo mysql-apt-config mysql-apt-config/enable-repo select mysql-5.6 | sudo debconf-set-selections
dpkg --configure -a
Don't forget to check your MySQL Version!
Thanks to you!