Previously it would only print a version when the tree was dirty. Fix it
so that it will also print one on a clean tree.
Tested:
- Built it from a committed tree:
$ hack/build-go.sh
$ output/go/bin/kubelet -version
Kubernetes version 0.1, build a091590dd10c
Signed-off-by: Filipe Brandenburger <filbranden@google.com>