generic: update for upstream driver specification

Signed-off-by: Evan Hazlett <ejhazlett@gmail.com>

libmachine/provision/ubuntu.go

@@ -75,7 +75,7 @@ func (provisioner *UbuntuProvisioner) Package(name string, action pkgaction.Pack
 
 func (provisioner *UbuntuProvisioner) dockerDaemonResponding() bool {
 	if _, err := provisioner.SSHCommand("sudo docker version"); err != nil {
-		log.Warn("Error getting SSH command to check if the daemon is up: %s", err)
+		log.Warnf("Error getting SSH command to check if the daemon is up: %s", err)
 		return false
 	}