bench: cluster patch

[Kirill-Churkin]

user@cartridge-cli % ./cartridge bench --leader=127.0.0.1:3301 --replica=127.0.0.1:3302
Tarantool 2.10.2 (Binary) b6820873-f007-4413-b2f0-69fe833c0e14 

Parameters:
        Leaders:
                127.0.0.1:3301
        Replicas:
                127.0.0.1:3302
        user: guest
        connections: 10
        simultaneous requests: 10
        duration: 10 seconds
        key size: 10 bytes
        data size: 20 bytes
        insert: 100 percentages
        select: 0 percentages
        update: 0 percentages

Data schema
| key                            | value
| ------------------------------ | ------------------------------
| random(10)                     | random(20)
Benchmark start
...
Benchmark stop.

Results:
        Success operations: 760386
        Failed  operations: 0
        Request count: 760474
        Time (seconds): 9.979464
        Requests per second: 76203

[Mons]

This should be better in tt, rather than in cartridge-cli

[sergos]

@LeonidVas please consider opportunity to transfer/adapt the test to tt perf bench.