Check if mkfs.btrfs exist

[anacelto]

Hi,

I was deploying concourse-worker on an Ubuntu 18.04.04 machine. I decide to go for btrfs filesystem for worker volume.

Ansible failed because mkfs.btrfs command was not found.

Should we verify that btrfs-progs package is installed before try to create the filesystem? I can do a PR if you agree.

Regards

[troykinsella]

Thanks for the suggestion! Yes, installing the appropriate required packages if the btrfs driver is selected makes sense to me. A PR would be appreciated.