ModeShape's fork channel prevents multiple clustered repositories from starting

After the implementation of https://issues.jboss.org/browse/MODE-2079 ModeShape uses a fork off of Infinispan JGroup's stack to send messages in a cluster. However, forks in JGroups are basically "named channels" and at the moment ModeShape uses the same (hardcoded) name for all the forks.
This presents problems when multiple, separate clustered repositories need to be started using the same JGroups stack.

We should also investigate and make sure that the JGroups cluster-wide lock, which is used during repository initialization, works correctly in this case.