integration tests for consul namer

[olix0r]

We should add integration tests (i.e under namer/consul/src/integration) that exercise end-to-end interactions with a real consul server.

Ideally:

1. Build a consul namer from configuration yaml
2. register services into consul
3. exercise that naming works properly
4. update service registration in consul
5. ensure updates
6. check that stats were recorded properly.

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