new "image" mount type

Add a new "image" mount type to `--mount`.  The source of the mount is
the name or ID of an image.  The destination is the path inside the
container.  Image mounts further support an optional `rw,readwrite`
parameter which if set to "true" will yield the mount writable inside
the container.  Note that no changes are propagated to the image mount
on the host (which in any case is read only).

Mounts are overlay mounts.  To support read-only overlay mounts, vendor
a non-release version of Buildah.

Signed-off-by: Valentin Rothberg <rothberg@redhat.com>

vendor/github.com/containers/buildah/imagebuildah/executor.go

@@ -26,7 +26,6 @@ import (
 	"github.com/containers/storage/pkg/archive"
 	digest "github.com/opencontainers/go-digest"
 	v1 "github.com/opencontainers/image-spec/specs-go/v1"
-	"github.com/opencontainers/runc/libcontainer/configs"
 	"github.com/openshift/imagebuilder"
 	"github.com/openshift/imagebuilder/dockerfile/parser"
 	"github.com/pkg/errors"
@@ -98,7 +97,7 @@ type Executor struct {
 	excludes                       []string
 	unusedArgs                     map[string]struct{}
 	capabilities                   []string
-	devices                        []configs.Device
+	devices                        buildah.ContainerDevices
 	signBy                         string
 	architecture                   string
 	timestamp                      *time.Time
@@ -130,7 +129,7 @@ func NewExecutor(store storage.Store, options BuildOptions, mainNode *parser.Nod
 		return nil, err
 	}
 
-	devices := []configs.Device{}
+	devices := buildah.ContainerDevices{}
 	for _, device := range append(defaultContainerConfig.Containers.Devices, options.Devices...) {
 		dev, err := parse.DeviceFromPath(device)
 		if err != nil {