Await thread pool termination when closing Pulsar client (#7962)

Co-authored-by: NJerry Peng <jerryp@splunk.com>

pulsar-client/src/main/java/org/apache/pulsar/client/util/ExecutorProvider.java

@@ -25,10 +25,13 @@ import java.util.List;
 import java.util.concurrent.ExecutorService;
 import java.util.concurrent.Executors;
 import java.util.concurrent.ThreadFactory;
+import java.util.concurrent.TimeUnit;
 import java.util.concurrent.atomic.AtomicInteger;
 
 import com.google.common.collect.Lists;
+import lombok.extern.slf4j.Slf4j;
 
+@Slf4j
 public class ExecutorProvider {
     private final int numThreads;
     private final List<ExecutorService> executors;
@@ -49,6 +52,13 @@ public class ExecutorProvider {
     }
 
     public void shutdownNow() {
-        executors.forEach(executor -> executor.shutdownNow());
+        executors.forEach(executor -> {
+            executor.shutdownNow();
+            try {
+                executor.awaitTermination(10, TimeUnit.SECONDS);
+            } catch (InterruptedException e) {
+                log.warn("Shutdown of thread pool was interrupted");
+            }
+        });
     }
 }