[fix][client] Fix orphan consumer when reconnection and closing are c…

…oncurrency executing (apache#22958)

(cherry picked from commit 69b2739)

pulsar-client/src/main/java/org/apache/pulsar/client/impl/ConsumerImpl.java

@@ -1060,7 +1060,7 @@ public void connectionFailed(PulsarClientException exception) {
     }
 
     @Override
-    public CompletableFuture<Void> closeAsync() {
+    public synchronized CompletableFuture<Void> closeAsync() {
         CompletableFuture<Void> closeFuture = new CompletableFuture<>();
 
         if (getState() == State.Closing || getState() == State.Closed) {