Time-out errors appear and the transactions‘ processing is delayed when testing with large scale transactions

[panyu4]

Context

When supporting the long time testing or running with a large scale txNumber, Caliper appears the below two phenomena：

1. The transactions sent by the clients are unable to be handled immediately by the back-end systems. Caliper will return the transactions' status success or fail until all of the transactions are generated and submitted to the corresponding back-end's system.
2. Since so many transactions are not handled immediately, the time-out errors appear frequently.

These phenomena might be caused by the clients' performance. Because when we test with the high performance CPU, they will disappear.

Expected Behavior

1. After sending the few transactions, the clients should handle the transactions and generate the new workloads simultaneously ;
2. Time-out errors should not appear in the long time test or large scale transactions' test.

Possible Fix

1. Try to let the client stop sending the transactions and make the cpu be able to interact with the back-end system;
2. add a new mode (eg. submitting the transactions' file to the back-end system ) to support the long time test or large scale transactions' test.

Exist Issues

#110

[feihujiang]

Now caliper is able to support fabric v1.1~v1.2 to pass the large scale tests (6.5 million transactions).