fix: TOOLS-2961 Warning should be based transaction_worker_threads and not on n_threads

[a-spiker]

The Transaction workers considered at

aerospike-benchmark/src/main/coordinator.c

Line 126 in 3e49d3c

uint32_t n_threads = args->n_threads;

which is transaction_workers + 1 [1 logging thread - 16 worker threads].

aerospike-benchmark/src/main/benchmark.c

Line 414 in 3e49d3c

n_threads = 1 + cdata->transaction_worker_threads;

To fix the default warning of
WARN --keys is not divisible by (--batch-write-size * --threads) so more than --keys records will be written

setting the warning logic based on transaction_worker_threads and not using n_threads

[a-spiker]

warning should be based on transaction_worker_threads and not on n_threads which is transaction_worker_threads + 1

[sunilvirus]

This change is better than the previous one.

[dwelch-spike]

Nice! LGTM