[VOL-2193] Create mocks for Kafka Client and Etcd

This commit consists of:
1) A kafka client mock that implements the kafka client interface
under voltha-lib-go/pkg/kafka/client.go
2) An embedded Etcd server that runs in-process and represents an
Etcd server.

Change-Id: I52a36132568e08c596bb4136918bebcb654a3b99
795 files changed
tree: 95a01609b29c0185654993a1baebc43356ed606e
  1. .gitignore
  2. .gitreview
  3. Makefile
  4. VERSION
  5. go.mod
  6. go.sum
  7. pkg/
  8. vendor/