Make sure instances have unique names.

Make sure we don't return an old docker client.

provisioner/dind.go

@@ -15,6 +15,7 @@ import (
 	"github.com/play-with-docker/play-with-docker/pwd/types"
 	"github.com/play-with-docker/play-with-docker/router"
 	"github.com/play-with-docker/play-with-docker/storage"
+	"github.com/rs/xid"
 )
 
 type DinD struct {
@@ -58,7 +59,7 @@ func (d *DinD) InstanceNew(session *types.Session, conf types.InstanceConfig) (*
 		}
 		conf.Hostname = nodeName
 	}
-	containerName := fmt.Sprintf("%s_%s", session.Id[:8], conf.Hostname)
+	containerName := fmt.Sprintf("%s_%s", session.Id[:8], xid.New().String())
 	opts := docker.CreateContainerOpts{
 		Image:         conf.ImageName,
 		SessionId:     session.Id,