Allow githost runners to support overlayfs option

Customer Ticket: https://gitlab.zendesk.com/agent/tickets/54824

Currently githost provided runners do not support overlayfs:

root@runner-for-1659:~# docker info Containers: 3 Running: 1 Paused: 0 Stopped: 2 Images: 4 Server Version: 1.12.5 Storage Driver: aufs Root Dir: /var/lib/docker/aufs Backing Filesystem: extfs Dirs: 37 Dirperm1 Supported: true Logging Driver: json-file Cgroup Driver: cgroupfs Plugins: Volume: local Network: host bridge overlay null Swarm: inactive Runtimes: runc Default Runtime: runc Security Options: apparmor Kernel Version: 4.4.0-53-generic Operating System: Ubuntu 14.04.5 LTS OSType: linux Architecture: x86_64 CPUs: 1 Total Memory: 992.6 MiB Name: default-runner-runner-for-1659 ID: DBPZ:XZX3:NGHM:CIMU:5GUV:G4VK:ENGG:263K:5RUD:DW2H:2IQJ:7LXX Docker Root Dir: /var/lib/docker Debug Mode (client): false Debug Mode (server): false Registry: https://index.docker.io/v1/ WARNING: No swap limit support Insecure Registries: 127.0.0.0/8

root@runner-for-1659:~# lsmod | grep overlay