VOL-2098 Support for Kafka liveness testing

* Adds liveness channel to sarama_client and kafka_interadapter proxy.
The liveness channel will push true or false to the channel on
each successful or failed Kafka publish.

* Adds support to make a "liveness publish attempt", which publishes
an empty message on a _liveness channel.

* Adds ServiceStatusNotReady to Probe

* Suppresses multiple Probe.UpdateStatus of the same status

* Adds the ability to attach a Probe to the grpc server, so that
when the probe returns NotReady, the Server responds to requests
with UNAVAILABLE.

Change-Id: I996c719570a50f2f6f397887d10d489608269c3f
diff --git a/pkg/grpc/common_test.go b/pkg/grpc/common_test.go
new file mode 100644
index 0000000..6ed7b26
--- /dev/null
+++ b/pkg/grpc/common_test.go
@@ -0,0 +1,44 @@
+/*
+ * Copyright 2019-present Open Networking Foundation
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package grpc
+
+import (
+	"github.com/opencord/voltha-lib-go/v2/pkg/log"
+)
+
+const (
+	/*
+	 * This sets the LogLevel of the Voltha logger. It's pinned to FatalLevel here, as we
+	 * generally don't want to see logger output, even when running go test in verbose
+	 * mode. Even "Error" level messages are expected to be output by some unit tests.
+	 *
+	 * If you are developing a unit test, and experiencing problems or wish additional
+	 * debugging from Voltha, then changing this constant to log.DebugLevel may be
+	 * useful.
+	 */
+
+	VOLTHA_LOGLEVEL = log.FatalLevel
+)
+
+// Unit test initialization. This init() function handles all unit tests in
+// the current directory.
+func init() {
+	// Logger must be configured or bad things happen
+	_, err := log.SetDefaultLogger(log.JSON, VOLTHA_LOGLEVEL, log.Fields{"instanceId": 1})
+	if err != nil {
+		panic(err)
+	}
+}