make invokes concurrent

In pre-v1.0 release couple of things prevented chaincodes invocations from being concurrently executed

• CC execution was pre consensus and so the order of execution has to be fixed across all chaincode invokes, across all peers
• (related to the above) read/writes to the ledger was for committing and not "simulation" and state versioning was not in place. Ledger required serial access

Given these restrictions are no longer enforced for 1.0, we can execute invokes in parallel and any non-deterministic results will be filtered before consensus.