Drop duplicate mounts of CNI directories.

Previously we had:
```
config:
  binds:
  - /var/lib/cni/conf:/etc/cni/net.d:rshared,rbind
  - /var/lib/cni/bin:/opt/cni/bin:rshared,rbind
  ...
  runtime:
    mounts:
    - type: bind
      source: /var/lib/cni/bin
      destination: /opt/cni/bin
      options: ["rw","bind"]
    - type: bind
      source: /var/lib/cni/conf
      destination: /etc/cni/net.d
      options: ["rw","bind"]
```

Which is redundant. Drop `runtime.mounts` to leave just the `binds`.

Signed-off-by: Ian Campbell <ijc@docker.com>

Author: Ian Campbell

pkg/kubelet/build.yml

@@ -36,12 +36,3 @@ config:
     - /var/lib/cni/bin
     - /var/lib/kubelet-plugins
     - /var/lib/nfs/statd/sm
-    mounts:
-    - type: bind
-      source: /var/lib/cni/bin
-      destination: /opt/cni/bin
-      options: ["rw","bind"]
-    - type: bind
-      source: /var/lib/cni/conf
-      destination: /etc/cni/net.d
-      options: ["rw","bind"]