Run generation continuously

**Describe the solution you'd like**
We would like to be able to run tests continuously.

**Describe alternatives you've considered**
As for now, we probably can use `--durration` option with a high number.

**Additional context**
We would like to be able to spin-up a Docker container which will work just a load producer and it should run until terminated. An option like `loop` or a behavior like when `--duration` is not defined should permit application to run until stopped.

As for now, it is not clear how `--duration` works - please see [Duration is ignored when run in replay-file mode #3](3)

Inspect the CLI handling of `--duration` and replay-file mode, then read issue #3 for the reported duration behavior. Define completion as a Docker load producer that keeps generating until terminated, with clear semantics for an omitted or loop-style duration option.

Written by the indexing model from the issue text.