switch to go vendoring

vendor/github.com/rs/xid/hostid_linux.go

@@ -0,0 +1,13 @@
+// +build linux
+
+package xid
+
+import "io/ioutil"
+
+func readPlatformMachineID() (string, error) {
+	b, err := ioutil.ReadFile("/etc/machine-id")
+	if err != nil || len(b) == 0 {
+		b, err = ioutil.ReadFile("/sys/class/dmi/id/product_uuid")
+	}
+	return string(b), err
+}