Clustering : TransactionProxy should support the ability to accept a local ThreePhaseCommitCohort actor path for forward compatibility

In Helium when the ShardTransaction processes a Ready message it sends back a the path of a ThreePhaseCommitCohort actor in the ReadyReply. This path is actually a local actor path, this local actor path is then converted into a remote path by the TransactionProxy.

The fix for CONTROLLER-720 breaks this capability which is required to support forward compatibility in a cluster where a transaction request originates in a node that has been upgraded to Helium-1 and the actual transaction is happening on a node which has not yet been upgraded to Helium-1.