Report offline peers to agents (#728)

The peer login expiration ACL check introduced in #714
filters out peers that are expired and agents receive a network map 
without that expired peers.
However, the agents should see those peers in status "Disconnected".

This PR extends the Agent <-> Management protocol 
by introducing a new field OfflinePeers
that contain expired peers. Agents keep track of those and display 
then just in the Status response.

client/internal/peer/status.go

@@ -55,6 +55,7 @@ type Status struct {
 	signal       SignalState
 	management   ManagementState
 	localPeer    LocalPeerState
+	offlinePeers []State
 }
 
 // NewRecorder returns a new Status instance
@@ -62,9 +63,18 @@ func NewRecorder() *Status {
 	return &Status{
 		peers:        make(map[string]State),
 		changeNotify: make(map[string]chan struct{}),
+		offlinePeers: make([]State, 0),
 	}
 }
 
+// ReplaceOfflinePeers replaces
+func (d *Status) ReplaceOfflinePeers(replacement []State) {
+	d.mux.Lock()
+	defer d.mux.Unlock()
+	d.offlinePeers = make([]State, len(replacement))
+	copy(d.offlinePeers, replacement)
+}
+
 // AddPeer adds peer to Daemon status map
 func (d *Status) AddPeer(peerPubKey string) error {
 	d.mux.Lock()
@@ -74,7 +84,7 @@ func (d *Status) AddPeer(peerPubKey string) error {
 	if ok {
 		return errors.New("peer already exist")
 	}
-	d.peers[peerPubKey] = State{PubKey: peerPubKey}
+	d.peers[peerPubKey] = State{PubKey: peerPubKey, ConnStatus: StatusDisconnected}
 	return nil
 }
 
@@ -237,5 +247,7 @@ func (d *Status) GetFullStatus() FullStatus {
 		fullStatus.Peers = append(fullStatus.Peers, status)
 	}
 
+	fullStatus.Peers = append(fullStatus.Peers, d.offlinePeers...)
+
 	return fullStatus
 }