[FAB-5498] Missing RLock in onStatusChangeFactory

There is a map access that isn't protected by a lock
that was introduced in a recent commit.

Change-Id: I31f884f76aaf0ba4a6b547c66830d8cd652f3c4e
Signed-off-by: yacovm <[email protected]>

Author: yacovm

gossip/service/gossip_service.go

@@ -283,7 +283,9 @@ func (g *gossipServiceImpl) onStatusChangeFactory(chainID string, committer bloc
 	return func(isLeader bool) {
 		if isLeader {
 			yield := func() {
+				g.lock.RLock()
 				le := g.leaderElection[chainID]
+				g.lock.RUnlock()
 				le.Yield()
 			}
 			logger.Info("Elected as a leader, starting delivery service for channel", chainID)