The test repeatedly induces failovers on the coordinator shard. Currently, it's possible for all three nodes to run for election and therefore refuse to vote for anyone but themselves, and mongos times out after waiting for 20 seconds for the coordinator shard to have a primary.

One idea is to only make two of the three replica nodes in the coordinator shard electable. The third replica node should then act as an "arbiter" in elections and vote for one of the other two.