Cannot benchmark multi-node cluster with benchmark-only pipeline

[danielmitterdorfer]

Rally version: 0.9.2

Observed behavior

When running a benchmark-only pipeline, e.g. esrally --pipeline=benchmark-only --test-mode --target-hosts="192.168.1.103:9200,192.168.1.103:9201", the benchmark will hang.

The logs show:

2018-02-22 16:47:35,780 PID:10549 rally.mechanic INFO Cluster will not be provisioned by Rally.
...
2018-02-22 16:47:35,793 PID:10615 rally.mechanic INFO Connecting to externally provisioned nodes on [[{'host': '192.168.1.103', 'port': 9200}, {'host': '192.168.1.103', 'port': 9201}]].
...
2018-02-22 16:47:35,929 PID:10549 rally.actor INFO [1] of [2] child actors have responded for transition from [starting] to [nodes_started].

Expected behavior

Rally should execute the benchmark against the multi-node cluster similarly to other situations.