[CLIENT] Unknown node version should be a lower bound

Today when we start a `TransportClient` we use the given transport
addresses and create a `DiscoveryNode` from it without knowing the
actual nodes version. We just use the `Version.CURRENT` which is an
upper bound. Yet, the other node might be a version less than the
currently running and serialisation of the nodes info might break. We
should rather use a lower bound here which is the version of the first
release with the same major version as `Version.CURRENT` since this is
what we officially support.

This commit moves to use the minimum major version or an RC / Snapshot
if the current version is a snapshot.

Closes #6894
can we remove this additional line (unless there was a specific reason why you added it)? ;)