JGroupsTransport should expose the cluster view information atomically

Currently the view is updated while holding a lock, but reading the view id, members, or coordinator is done without a lock. This means when a thread sends a request and receives a SuspectException, it cannot simply wait for a new view before retrying: the initial request may have used the latest view, and only the members list could be outdated (even if read later).

To allow atomically reading the view id and the member list, we should use an immutable structure similar to CacheTopology.