Replace paranoid mode with three pools and per-pool maximum failure ratio.

Three pools are used: --pal_pool, --neutral_pool, --foe_pool.

Per-pool:
  - one random server is tried until success
  - first successful result is used
  - a maximum failure ratio before giving up can be passed
    with --allowed_per_pool_failure_ratio

The median of the per-pool results is used.