VOL-1867 move simulated olt from voltha-go to voltha-simolt-adapter

Sourced from voltha-go commit 251a11c0ffe60512318a644cd6ce0dc4e12f4018

Change-Id: I8e7ee4da1fed739b3c461917301d2729a79307f5
diff --git a/vendor/github.com/rcrowley/go-metrics/metrics.go b/vendor/github.com/rcrowley/go-metrics/metrics.go
new file mode 100644
index 0000000..b97a49e
--- /dev/null
+++ b/vendor/github.com/rcrowley/go-metrics/metrics.go
@@ -0,0 +1,13 @@
+// Go port of Coda Hale's Metrics library
+//
+// <https://github.com/rcrowley/go-metrics>
+//
+// Coda Hale's original work: <https://github.com/codahale/metrics>
+package metrics
+
+// UseNilMetrics is checked by the constructor functions for all of the
+// standard metrics.  If it is true, the metric returned is a stub.
+//
+// This global kill-switch helps quantify the observer effect and makes
+// for less cluttered pprof profiles.
+var UseNilMetrics bool = false