FIX: allow overlayfs storage driver (#1014)

new storage driver on by default, per:
https://docs.docker.com/engine/storage/drivers/

containerd image store seems to report as overlayfs, so we should allow for this
string as well.

Ref:
https://meta.discourse.org/t/overlayfs-to-overlay2-failed-on-fresh-installation-storage-driver/389126

Author: featheredtoast

launcher

@@ -208,7 +208,7 @@ check_prereqs() {
   fi
 
   # 2. running an approved storage driver?
-  if ! $docker_path info 2> /dev/null | grep -E -q 'Storage Driver: (btrfs|aufs|zfs|overlay2)$'; then
+  if ! $docker_path info 2> /dev/null | grep -E -q 'Storage Driver: (btrfs|aufs|zfs|overlay2|overlayfs)$'; then
     echo "Your Docker installation is not using a supported storage driver.  If we were to proceed you may have a broken install."
     echo "overlay2 is the recommended storage driver, although zfs and aufs may work as well."
     echo "Other storage drivers are known to be problematic."