Add vendoring to containerd master

Initial vendor list validated with empty $GOPATH
and only master checked out; followed by `make`
and verified that all binaries build properly.
Updates require github.com/LK4D4/vndr tool.

Signed-off-by: Phil Estes <estesp@linux.vnet.ibm.com>

vendor/github.com/docker/go-metrics/unit.go

@@ -0,0 +1,12 @@
+package metrics
+
+// Unit represents the type or precision of a metric that is appended to
+// the metrics fully qualified name
+type Unit string
+
+const (
+	Nanoseconds Unit = "nanoseconds"
+	Seconds     Unit = "seconds"
+	Bytes       Unit = "bytes"
+	Total       Unit = "total"
+)