server: use chanInfo instead of chanPolicy to establish channel peer conns

In this commit, we modify the way we attempt to locate the our channel
peer to establish a persistent connection on start up. Before this
commit, we would use the channel policy pointing to the peer to locate
the node as it's embedded in the struct. However, at times it's
currently possible for the channel policy to not be found in the
database if the remote nodes announces before we finalize the process on
our end. This can at times lead to a panic as the pointer isn't checked
before attempting to access it.

To remedy this, we now instead use the channel info which will _always_
be there if the channel is known.

Author: Roasbeef

server.go

@@ -1651,19 +1651,39 @@ func (s *server) establishPersistentConnections() error {
 	if err != nil {
 		return err
 	}
+
 	// TODO(roasbeef): instead iterate over link nodes and query graph for
 	// each of the nodes.
+	selfPub := s.identityPriv.PubKey().SerializeCompressed()
 	err = sourceNode.ForEachChannel(nil, func(
-		_ *bbolt.Tx,
-		_ *channeldb.ChannelEdgeInfo,
+		tx *bbolt.Tx,
+		chanInfo *channeldb.ChannelEdgeInfo,
 		policy, _ *channeldb.ChannelEdgePolicy) error {
 
-		pubStr := string(policy.Node.PubKeyBytes[:])
+		// If the remote party has announced the channel to us, but we
+		// haven't yet, then we won't have a policy. However, we don't
+		// need this to connect to the peer, so we'll log it and move on.
+		if policy == nil {
+			srvrLog.Warnf("No channel policy found for "+
+				"ChannelPoint(%v): ", chanInfo.ChannelPoint)
+		}
+
+		// We'll now fetch the peer opposite from us within this
+		// channel so we can queue up a direct connection to them.
+		channelPeer, err := chanInfo.FetchOtherNode(tx, selfPub)
+		if err != nil {
+			return fmt.Errorf("unable to fetch channel peer for "+
+				"ChannelPoint(%v): %v", chanInfo.ChannelPoint,
+				err)
+		}
+
+		pubStr := string(channelPeer.PubKeyBytes[:])
 
-		// Add all unique addresses from channel graph/NodeAnnouncements
-		// to the list of addresses we'll connect to for this peer.
+		// Add all unique addresses from channel
+		// graph/NodeAnnouncements to the list of addresses we'll
+		// connect to for this peer.
 		addrSet := make(map[string]net.Addr)
-		for _, addr := range policy.Node.Addresses {
+		for _, addr := range channelPeer.Addresses {
 			switch addr.(type) {
 			case *net.TCPAddr:
 				addrSet[addr.String()] = addr
@@ -1705,7 +1725,7 @@ func (s *server) establishPersistentConnections() error {
 		n := &nodeAddresses{
 			addresses: addrs,
 		}
-		n.pubKey, err = policy.Node.PubKey()
+		n.pubKey, err = channelPeer.PubKey()
 		if err != nil {
 			return err
 		}