[#749] morph: Fix panic when closing morph client

Signed-off-by: Anton Nikiforov <an.nikiforov@yadro.com>

pkg/morph/client/client.go

@@ -73,6 +73,8 @@ type Client struct {
 
 	// channel for internal stop
 	closeChan chan struct{}
+	closed    atomic.Bool
+	wg        sync.WaitGroup
 
 	// indicates that Client is not able to
 	// establish connection to any of the