Docker 17.11.0 requires cgroup_enable=memory on grub

[miguelsimoes]

To start the development environment, we will need to change grub configuration. For that, we require the following steps:

1. Start vagrant with vagrant up
   1.1. It will show errors when starting the docker engine
2. Enter the instance with vagrant ssh
3. Edit file /etc/default/grub
4. Change the line from GRUB_CMDLINE_LINUX_DEFAULT="quiet " to
   GRUB_CMDLINE_LINUX_DEFAULT="quiet cgroup_enable=memory"
5. Save and exit
6. Run sudo update-grub2
7. Restart the vagrant instance with vagrant reload --provision

With this, all will go well.

NOTE: This needs to be changed so it does not require a failed boot before it will run properly.