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/seccomp_unsupported.go

@@ -0,0 +1,15 @@
+// +build !seccomp !linux
+
+package buildah
+
+import (
+	"github.com/opencontainers/runtime-spec/specs-go"
+)
+
+func setupSeccomp(spec *specs.Spec, seccompProfilePath string) error {
+	if spec.Linux != nil {
+		// runtime-tools may have supplied us with a default filter
+		spec.Linux.Seccomp = nil
+	}
+	return nil
+}