Update containerd to ec15fe95aa.

Signed-off-by: Lantao Liu <lantaol@google.com>

vendor/github.com/Microsoft/hcsshim/guid.go

@@ -0,0 +1,19 @@
+package hcsshim
+
+import (
+	"crypto/sha1"
+	"fmt"
+)
+
+type GUID [16]byte
+
+func NewGUID(source string) *GUID {
+	h := sha1.Sum([]byte(source))
+	var g GUID
+	copy(g[0:], h[0:16])
+	return &g
+}
+
+func (g *GUID) ToString() string {
+	return fmt.Sprintf("%02x%02x%02x%02x-%02x%02x-%02x%02x-%02x-%02x", g[3], g[2], g[1], g[0], g[5], g[4], g[7], g[6], g[8:10], g[10:])
+}