Use buildah commit and bud in podman

Vendor in buildah and use as much of commit and bug as possible for podman
build and commit.

Resolves #586
Signed-off-by: baude <bbaude@redhat.com>

Closes: #681
Approved by: mheon

vendor/github.com/projectatomic/buildah/util.go

@@ -0,0 +1,34 @@
+package buildah
+
+import (
+	"github.com/containers/storage/pkg/chrootarchive"
+	"github.com/containers/storage/pkg/reexec"
+)
+
+var (
+	// CopyWithTar defines the copy method to use.
+	copyWithTar     = chrootarchive.NewArchiver(nil).CopyWithTar
+	copyFileWithTar = chrootarchive.NewArchiver(nil).CopyFileWithTar
+	untarPath       = chrootarchive.NewArchiver(nil).UntarPath
+)
+
+// InitReexec is a wrapper for reexec.Init().  It should be called at
+// the start of main(), and if it returns true, main() should return
+// immediately.
+func InitReexec() bool {
+	return reexec.Init()
+}
+
+func copyStringStringMap(m map[string]string) map[string]string {
+	n := map[string]string{}
+	for k, v := range m {
+		n[k] = v
+	}
+	return n
+}
+
+func copyStringSlice(s []string) []string {
+	t := make([]string, len(s))
+	copy(t, s)
+	return t
+}