Load kernel modules automatically inside a kube-proxy pod

This change will mount `/lib/modules` on host to the kube-proxy pod,
so that a kube-proxy pod can load kernel modules by need
or when `modprobe <kmod>` is run inside the pod.

This will be convenient for kube-proxy running in IPVS mode.
Users will don't have to run `modprobe ip_vs` on nodes before starting
a kube-proxy pod.

cluster/addons/kube-proxy/kube-proxy-ds.yaml

@@ -53,6 +53,9 @@ spec:
         - mountPath: /run/xtables.lock
           name: xtables-lock
           readOnly: false
+        - mountPath: /lib/modules
+          name: lib-modules
+          readOnly: true
       volumes:
       - name: varlog
         hostPath:
@@ -64,4 +67,7 @@ spec:
         hostPath:
           path: /run/xtables.lock
           type: FileOrCreate
+      - name: lib-modules
+        hostPath:
+          path: /lib/modules
       serviceAccountName: kube-proxy

cluster/saltbase/salt/kube-proxy/kube-proxy.manifest

@@ -96,6 +96,9 @@ spec:
     - mountPath: /run/xtables.lock
       name: iptableslock
       readOnly: false
+    - mountPath: /lib/modules
+      name: lib-modules
+      readOnly: true
   volumes:
   - hostPath:
       path: /usr/share/ca-certificates
@@ -114,3 +117,6 @@ spec:
       path: /run/xtables.lock
       type: FileOrCreate
     name: iptableslock
+  - name: lib-modules
+    hostPath:
+      path: /lib/modules