cluster: bump kubelets to 1.14.3

Change-Id: I02ed978a49629cdfc3f3587ad640e8cc5a5fad23
diff --git a/cluster/nix/module-kubernetes.nix b/cluster/nix/module-kubernetes.nix
index 1e71ada..420b32d 100644
--- a/cluster/nix/module-kubernetes.nix
+++ b/cluster/nix/module-kubernetes.nix
@@ -11,10 +11,10 @@
   }) {};
   # Pin for kubelet
   k8spkgsKubelet = import (fetchGit {
-    # Now at 1.13.5
-    name = "nixos-unstable-2019-04-12";
+    # Now at 1.14.3
+    name = "nixos-unstable-2019-06-17";
     url = https://github.com/nixos/nixpkgs-channels/;
-    rev = "1fc591f9a5bd1b016b5d66dfab29560073955a14";
+    rev = "415e8e5820b7825fb74a6c7986bf6af725227eaa";
   }) {};
 
 in rec {