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/armon/go-metrics/const_unix.go b/vendor/github.com/armon/go-metrics/const_unix.go
new file mode 100644
index 0000000..31098dd
--- /dev/null
+++ b/vendor/github.com/armon/go-metrics/const_unix.go
@@ -0,0 +1,12 @@
+// +build !windows
+
+package metrics
+
+import (
+	"syscall"
+)
+
+const (
+	// DefaultSignal is used with DefaultInmemSignal
+	DefaultSignal = syscall.SIGUSR1
+)