Add golint to test (#255)

* Add a new lint rule to the Makefile

Signed-off-by: Kenfe-Mickael Laventure <mickael.laventure@gmail.com>

* Fix linter errors

Signed-off-by: Kenfe-Mickael Laventure <mickael.laventure@gmail.com>

* Allow replacing the default apt mirror

Signed-off-by: Kenfe-Mickael Laventure <mickael.laventure@gmail.com>

hack/validate-lint

@@ -0,0 +1,9 @@
+#!/bin/bash
+
+lint_error=$(golint ./... | grep -v vendor | grep -v .pb. | tee /dev/stderr)
+
+if [ "$lint_error" != "" ]; then
+	exit 1
+fi
+
+exit 0