[VOL-4514]  Addressing device reconciliation failure

This commit consists of augmention the current GetHeathStatus()
API on the grpc server with the grpc client information.  This
provides the grpc server with more insights of the grpc client
connection status.  This is useful for a server to know whether it
is more likely to receive a response following a request from a
remote server, represented by the grpc client(s).  For now this is
used by the openonu adapter to figure out when it can send an
OMCI request to the openolt adapter following a restart of the
onu adapter.

Change-Id: I0c117c0002b83606b95d7269e6f53d21941e4ba5
diff --git a/protos/voltha_protos/common.proto b/protos/voltha_protos/common.proto
index 9efbdd9..f7efff6 100755
--- a/protos/voltha_protos/common.proto
+++ b/protos/voltha_protos/common.proto
@@ -20,6 +20,18 @@
     api_test=0;
 }
 
+message Connection {
+    // endpoint is the endpoint sending the request
+    string endpoint = 1;
+
+    // contextInfo represents additional contextual information
+    string contextInfo = 2;
+
+    // keep_alive_interval is used to indicate to the remote endpoint how often it 
+    // will get a keep alive notification
+    int64 keep_alive_interval = 3;
+}
+
 message AdminState {
     // Administrative State
     enum Types {