Vendor in latest containers/buildah

Switch from projectatomic/buildah to containers/buildah

Signed-off-by: Daniel J Walsh <dwalsh@redhat.com>

vendor/github.com/containers/buildah/delete.go

@@ -0,0 +1,18 @@
+package buildah
+
+import (
+	"github.com/opencontainers/selinux/go-selinux/label"
+	"github.com/pkg/errors"
+)
+
+// Delete removes the working container.  The buildah.Builder object should not
+// be used after this method is called.
+func (b *Builder) Delete() error {
+	if err := b.store.DeleteContainer(b.ContainerID); err != nil {
+		return errors.Wrapf(err, "error deleting build container")
+	}
+	b.MountPoint = ""
+	b.Container = ""
+	b.ContainerID = ""
+	return label.ReleaseLabel(b.ProcessLabel)
+}