clustermesh: Ignore ..data directory of secrets mount
clustermesh: Ignore ..data directory of secrets mount

Skip any directory present in the config directory to avoid warnings like these:
```
level=warning msg="Unable to establish etcd connection to remote cluser" clusterName=..data config=/var/lib/cilium/clustermesh/..data error="read /var/lib/cilium/clustermesh/..data: is a directory" kvstoreErr="<nil>" kvstoreStatus= subsys=clustermesh
```

Fixes: #6408

Signed-off-by: Thomas Graf <5f50a84c1fa3bcff146405017f36aec1a10a9e38@cilium.io>

cilium/cilium,michi-covalent/cilium,tklauser/cilium,tgraf/cilium,cilium/cilium,michi-covalent/cilium,tgraf/cilium,tgraf/cilium,tklauser/cilium,tgraf/cilium,cilium-team/cilium,michi-covalent/cilium,cilium/cilium,tklauser/cilium,tgraf/cilium,michi-covalent/cilium,michi-covalent/cilium,tgraf/cilium,tklauser/cilium,cilium/cilium,cilium/cilium,tklauser/cilium,cilium-team/cilium