Use anonymous volume for bundles dir

This allows the test suite to be able to run without worrying about
the underlying fs used by the container running the daemon (e.g.
aufs-on-aufs), so long as the host running the container is running a
supported fs.
The volume will be cleaned up when the container is removed due to
`--rm`.

Signed-off-by: Brian Goff <cpuguy83@gmail.com>

Makefile

@@ -54,6 +54,10 @@ DOCKER_ENVS := \
 BIND_DIR := $(if $(BINDDIR),$(BINDDIR),$(if $(DOCKER_HOST),,bundles))
 DOCKER_MOUNT := $(if $(BIND_DIR),-v "$(CURDIR)/$(BIND_DIR):/go/src/github.com/docker/docker/$(BIND_DIR)")
 
+# This allows the test suite to be able to run without worrying about the underlying fs used by the container running the daemon (e.g. aufs-on-aufs), so long as the host running the container is running a supported fs.
+# The volume will be cleaned up when the container is removed due to `--rm`.
+# Note that `BIND_DIR` will already be set to `bundles` if `DOCKER_HOST` is not set (see above BIND_DIR line), in such case this will do nothing since `DOCKER_MOUNT` will already be set.
+DOCKER_MOUNT := $(if $(DOCKER_MOUNT),$(DOCKER_MOUNT),-v "/go/src/github.com/docker/docker/bundles")
 
 GIT_BRANCH := $(shell git rev-parse --abbrev-ref HEAD 2>/dev/null)
 DOCKER_IMAGE := docker-dev$(if $(GIT_BRANCH),:$(GIT_BRANCH))