rpc: a link is now only active if it is eligible to forward HTLCs

In this commit, we further constrain the candidacy for an “active”
channel. In addition to being present within the link, it *must* also
have the RemoteNextRevocation set. Otherwise, this indicates that we
haven’t yet processed a FundingLocked message for this channel.

rpcserver.go

@@ -1465,8 +1465,11 @@ func (r *rpcServer) ListChannels(ctx context.Context,
 
 		channelID := lnwire.NewChanIDFromOutPoint(&chanPoint)
 		var linkActive bool
-		if _, err := r.server.htlcSwitch.GetLink(channelID); err == nil {
-			linkActive = true
+		if link, err := r.server.htlcSwitch.GetLink(channelID); err == nil {
+			// A channel is only considered active if it is known
+			// by the switch *and* able to forward
+			// incoming/outgoing payments.
+			linkActive = link.EligibleToForward()
 		}
 
 		// As this is required for display purposes, we'll calculate