[VOL-3860] redis client support in voltha-lib-go

redis client support has been added in this patch. There are two
types client `redis` and `redis-sentinel` to connect a redis instance.
redis-sentinel is required to be able to find the master redis
instance from a redis-sentinel process. See redis-sentinel usage
https://redis.io/topics/sentinel and
https://pkg.go.dev/github.com/go-redis/redis/v8#NewFailoverClient
for more information. If there is no need to have any failover
mechanism then the redis client type is the option to choose.

Change-Id: I997ed92115a9d565df632c6dd8184b9bab77b991
diff --git a/vendor/go.opentelemetry.io/otel/go.mod b/vendor/go.opentelemetry.io/otel/go.mod
new file mode 100644
index 0000000..95f9aa4
--- /dev/null
+++ b/vendor/go.opentelemetry.io/otel/go.mod
@@ -0,0 +1,8 @@
+module go.opentelemetry.io/otel
+
+go 1.14
+
+require (
+	github.com/google/go-cmp v0.5.2
+	github.com/stretchr/testify v1.6.1
+)