[FAB-4512] Add leader log entry in gossip

This commit adds a logging entry that specifies if the peer
is going to fetch blocks from the ordering service, or to abort
doing so.

Change-Id: I3d2fcd97e57f67e01ab9dacf52aed22e6f296ee9
Signed-off-by: Yacov Manevich <yacovm@il.ibm.com>

gossip/service/gossip_service.go

@@ -289,10 +289,12 @@ func (g *gossipServiceImpl) amIinChannel(myOrg string, config Config) bool {
 func (g *gossipServiceImpl) onStatusChangeFactory(chainID string, committer blocksprovider.LedgerInfo) func(bool) {
 	return func(isLeader bool) {
 		if isLeader {
+			logger.Info("Elected as a leader, starting delivery service for channel", chainID)
 			if err := g.deliveryService.StartDeliverForChannel(chainID, committer); err != nil {
 				logger.Error("Delivery service is not able to start blocks delivery for chain, due to", err)
 			}
 		} else {
+			logger.Info("Renounced leadership, stopping delivery service for channel", chainID)
 			if err := g.deliveryService.StopDeliverForChannel(chainID); err != nil {
 				logger.Error("Delivery service is not able to stop blocks delivery for chain, due to", err)
 			}