Gossip- Don't log sending to empty slice of peers

The code that uses the gossip comm layer's Send() method
computes dynamically a set of peers to send a message to,
usually out of a batch of all kinds of messages.

As a result, the peer set passed to the send method is sometimes empty.
This makes the gossip comm layer log something like "sending Msg M to 0 peers".

I added a check that makes the Send() function skip sending if the peer slice
passed is empty.

Signed-off-by: Yacov Manevich <yacovm@il.ibm.com>
Change-Id: I689f3163f496ac91629536e63a16d0e7effd99e3

Author: yacovm

gossip/comm/comm_impl.go

@@ -212,7 +212,7 @@ func (c *commImpl) createConnection(endpoint string, expectedPKIID common.PKIidT
 }
 
 func (c *commImpl) Send(msg *proto.GossipMessage, peers ...*RemotePeer) {
-	if c.isStopping() {
+	if c.isStopping() || len(peers) == 0 {
 		return
 	}