[Node] Address issue with underscore in chain name

[lazam]

K8s doesn't allow an underscore in pod name due to RFC 1123

a lowercase RFC 1123 label must consist of lower case alphanumeric characters or '-', and must start and end with an alphanumeric character (e.g. 'my-name', or '123-abc', regex used for validation is '[a-z0-9]([-a-z0-9]*[a-z0-9])?')

This prevents to easily use the node.chain variable for chain's with underscore in its name such as collectives_polkadot. The solution is to just replace it with - to conform with the standard in the pod name.