control/controlclient: allow multiple non-streaming map requests (#19106)

A client with an active streaming session would break if using the same
client for a non-streaming session. Allow the client 1 streaming and n
non-streaming sessions at the same time.

Fixes #19105

Signed-off-by: Claus Lensbøl <claus@tailscale.com>

control/controlclient/direct.go

@@ -1121,18 +1121,22 @@ func (c *Direct) sendMapRequest(ctx context.Context, isStreaming bool, nu Netmap
 		return nil
 	}
 
-	if c.streamingMapSession != nil {
+	if isStreaming && c.streamingMapSession != nil {
 		panic("mapSession is already set")
 	}
 
 	sess := newMapSession(persist.PrivateNodeKey(), nu, c.controlKnobs)
-	c.streamingMapSession = sess
-	defer func() {
-		sess.Close()
-		c.mu.Lock()
-		c.streamingMapSession = nil
-		c.mu.Unlock()
-	}()
+	if isStreaming {
+		c.streamingMapSession = sess
+		defer func() {
+			sess.Close()
+			c.mu.Lock()
+			c.streamingMapSession = nil
+			c.mu.Unlock()
+		}()
+	} else {
+		defer sess.Close()
+	}
 	sess.cancel = cancel
 	sess.logf = c.logf
 	sess.vlogf = vlogf