Apply isStateTransferEnabled attribute to consumer only

We needed to be able to configure state transfer providers and consumers separately. The short term strategy is to make each node a provider. We then use the 'fetchInMemoryState' attribute to determine if a node can be a consumer or not.

org.infinispan.factories.StateTransferManagerFactory

Updated to remove the 'isStateTransferEnabled' check. Now every node is a state transfer provider.

org.infinispan.statetransfer.StateTransferManagerImpl

public void start()

Updated to now check the 'fetchInMemoryState' attribute to determine if this node can operate as a consumer.

public void generateState()

Updated so that any node can generate the state.