Test load description should expose a Throughput and not a rate option

[sskhiri]

The Test description is currently taking a rate in msg/sec parameter. This is misleading since the internal RoQ througput is calculated by the number of pub and sub:

• Let x the number of pub
• Let y the number of sub
• Let r the rate in msg/sec

The Total throughput is = x.y.r message/s Then we should let the user enter the expected throughput, then we will deduce r=throughput/(x.y)

[sskhiri]

I added the throughput option. This option must be use only if rate = 0, Max sub and Max sub are non 0. "{\"maxPub\":5,\"duration\":5.0,\"rate\":3000,\"maxSub\":2,\"payload\":10,\"delay\":5,\"spawnRate\":8}"; or "{\"maxPub\":2,\"duration\":2.0,\"throughput\":36000,\"maxSub\":6,\"payload\":5,\"delay\":5,\"spawnRate\":1}";

Are the same test description.