TestCreateIndexThenFreezePlanThenAddNode intermittent failure

"make test" works on my dev box, but travis-CI reported a build failure due to an "offending" commit of merely updating a design writeup / text-document...

```
https://travis-ci.org/couchbaselabs/cbft/builds/72039708
```

Perhaps TestCreateIndexThenFreezePlanThenAddNode has race situations, and we got lucky to hit it on travis...

--- FAIL: TestCreateIndexThenFreezePlanThenAddNode-2 (0.02s)
rest_test.go:2492: expected same casPrev: 5, casCurr: 9
rest_test.go:2498: expected same plans, planPIndexesPrev: {"uuid":"173294f94dec4008","planPIndexes":{"myIdx_7737a58673fd58a1_83dcefb7":{"name":"myIdx_7737a58673fd58a1_83dcefb7","uuid":"4ce04a1f3b53b998","indexType":"bleve","indexName":"myIdx","indexUUID":"7737a58673fd58a1","indexParams":"","sourceType":"primary","sourceName":"","sourceUUID":"","sourceParams":"{\"numPartitions\":2}","sourcePartitions":"1","nodes":{"4caa300765b66578":{"canRead":true,"canWrite":true,"priority":0}}},"myIdx_7737a58673fd58a1_f4dbdf21":{"name":"myIdx_7737a58673fd58a1_f4dbdf21","uuid":"13842e570cc46e12","indexType":"bleve","indexName":"myIdx","indexUUID":"7737a58673fd58a1","indexParams":"","sourceType":"primary","sourceName":"","sourceUUID":"","sourceParams":"{\"numPartitions\":2}","sourcePartitions":"0","nodes":{"4caa300765b66578":{"canRead":true,"canWrite":true,"priority":0}}}},"implVersion":"3.1.0","warnings":{"myIdx":[]}}, planPIndexesCurr: {"uuid":"72332fcc15e188da","planPIndexes":{"myIdx_7737a58673fd58a1_83dcefb7":{"name":"myIdx_7737a58673fd58a1_83dcefb7","uuid":"11b343ee0258fdbf","indexType":"bleve","indexName":"myIdx","indexUUID":"7737a58673fd58a1","indexParams":"","sourceType":"primary","sourceName":"","sourceUUID":"","sourceParams":"{\"numPartitions\":2}","sourcePartitions":"1","nodes":{"4caa300765b66578":{"canRead":true,"canWrite":true,"priority":0}}},"myIdx_7737a58673fd58a1_f4dbdf21":{"name":"myIdx_7737a58673fd58a1_f4dbdf21","uuid":"1c6aad0424513a4b","indexType":"bleve","indexName":"myIdx","indexUUID":"7737a58673fd58a1","indexParams":"","sourceType":"primary","sourceName":"","sourceUUID":"","sourceParams":"{\"numPartitions\":2}","sourcePartitions":"0","nodes":{"622edd59f35eb1b7":{"canRead":true,"canWrite":true,"priority":0}}}},"implVersion":"3.1.0","warnings":{"myIdx":[]}}