The test runs sqlgen load against the cluster and in round robin order kills
and restarts nodes. After each transition consistency check is done. This
facilitates testing configration changes under highly concurrent load with lots
of certification conflicts.

Sometimes the first consistency check fails, perhaps due to some race
condition. In that case a second consistency check is attempted and if that
fails the script exits with error code.

Usage with gcomm backend:

./run.sh [N]

Usage with vsbes backend:

GCS_TYPE=vsbes VSBES_ADDRESS=192.168.0.1:5678 ./run.sh [N]

where N is the number of off/on transitions. I.e. N=1 means that 1 node will
be killed and restarted. If N is omitted it goes forever.