[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
diff --git a/vendor/github.com/grpc-ecosystem/go-grpc-middleware/.travis.yml b/vendor/github.com/grpc-ecosystem/go-grpc-middleware/.travis.yml
new file mode 100644
index 0000000..702fa5b
--- /dev/null
+++ b/vendor/github.com/grpc-ecosystem/go-grpc-middleware/.travis.yml
@@ -0,0 +1,21 @@
+sudo: false
+language: go
+go:
+  - 1.8.x
+env:
+  - DEP_VERSION="0.3.2"
+
+before_install:
+  # Download the binary to bin folder in $GOPATH
+  - curl -L -s https://github.com/golang/dep/releases/download/v${DEP_VERSION}/dep-linux-amd64 -o $GOPATH/bin/dep
+  # Make the binary executable
+  - chmod +x $GOPATH/bin/dep
+
+install:
+  - dep ensure
+
+script:
+ - make test
+ 
+after_success:
+  - bash <(curl -s https://codecov.io/bash)