update testing related dependencies

Signed-off-by: Davanum Srinivas <davanum@gmail.com>

vendor/github.com/nxadm/tail/tail_posix.go

@@ -0,0 +1,11 @@
+// +build !windows
+
+package tail
+
+import (
+	"os"
+)
+
+func OpenFile(name string) (file *os.File, err error) {
+	return os.Open(name)
+}