raft: return empty status if node is stopped

If the node is stopped, then Status can hang forever because there is no
event loop to answer. So, just return empty status to avoid deadlocks.

Fix #6855

Signed-off-by: Alexander Morozov <lk4d4math@gmail.com>

raft/node.go

@@ -462,8 +462,12 @@ func (n *node) ApplyConfChange(cc pb.ConfChange) *pb.ConfState {
 
 func (n *node) Status() Status {
 	c := make(chan Status)
-	n.status <- c
-	return <-c
+	select {
+	case n.status <- c:
+		return <-c
+	case <-n.done:
+		return Status{}
+	}
 }
 
 func (n *node) ReportUnreachable(id uint64) {