Report if Nebula start fails because of tun device name (#1588)

* specifically report if nebula start fails because of tun device name

* close all routines when closing the tun

interface.go

@@ -490,6 +490,14 @@ func (f *Interface) Close() error {
 			f.l.WithError(err).Error("Error while closing udp socket")
 		}
 	}
+	for i, r := range f.readers {
+		if i == 0 {
+			continue // f.readers[0] is f.inside, which we want to save for last
+		}
+		if err := r.Close(); err != nil {
+			f.l.WithError(err).Error("Error while closing tun reader")
+		}
+	}
 
 	// Release the tun device
 	return f.inside.Close()