I have a replicaset named rs0, with 2 members with 1 using priority 1. (I know it is not safe, it's a dev env) running inside docker containers and linked together.

On my app, I linked the MongoDB containers as mdb-1 and mdb-2:

`mongodb://mdb-1:27017,mdb-2:27017/dialonce?replicaSet=rs0`

Then I get the error:
```
[service-auth-3]2016-07-12T09:15:23.027769297Z error: MongoError: no primary found in replicaset
[service-auth-3]2016-07-12T09:15:23.027807154Z at /usr/src/app/node_modules/mongodb-core/lib/topologies/replset.js:533:32
[service-auth-3]2016-07-12T09:15:23.027812184Z at .<anonymous> (/usr/src/app/node_modules/mongodb-core/lib/topologies/replset.js:376:24)
[service-auth-3]2016-07-12T09:15:23.027815644Z at g (events.js:286:16)
[service-auth-3]2016-07-12T09:15:23.027818112Z at emitOne (events.js:96:13)
[service-auth-3]2016-07-12T09:15:23.027820600Z at emit (events.js:188:7)
[service-auth-3]2016-07-12T09:15:23.027823340Z at .<anonymous> (/usr/src/app/node_modules/mongodb-core/lib/topologies/server.js:289:21)
[service-auth-3]2016-07-12T09:15:23.027826240Z at emitOne (events.js:96:13)
[service-auth-3]2016-07-12T09:15:23.027828829Z at emit (events.js:188:7)
[service-auth-3]2016-07-12T09:15:23.027831867Z at .<anonymous> (/usr/src/app/node_modules/mongodb-core/lib/connection/pool.js:230:12)
[service-auth-3]2016-07-12T09:15:23.027836363Z at g (events.js:286:16)
[service-auth-3]2016-07-12T09:15:23.027838891Z at emitTwo (events.js:106:13)
[service-auth-3]2016-07-12T09:15:23.027841347Z at emit (events.js:191:7)
[service-auth-3]2016-07-12T09:15:23.027844241Z at Socket.<anonymous> (/usr/src/app/node_modules/mongodb-core/lib/connection/connection.js:150:49)
[service-auth-3]2016-07-12T09:15:23.027847013Z at Socket.g (events.js:286:16)
[service-auth-3]2016-07-12T09:15:23.027849441Z at emitOne (events.js:96:13)
[service-auth-3]2016-07-12T09:15:23.027853221Z at Socket.emit (events.js:188:7)
[service-auth-3]2016-07-12T09:15:23.027855762Z at connectErrorNT (net.js:1015:8)
```

It was working fine with 2.1.8, reverting to 2.1.8 fixes the issue.