[fix][broker] Fix the broker shutdown issue after Zookeeper node cras…

…hed (#17909)

(cherry picked from commit e26060a)

pulsar-metadata/src/main/java/org/apache/pulsar/metadata/impl/ZKMetadataStore.java

@@ -75,7 +75,7 @@ public ZKMetadataStore(String metadataURL, MetadataStoreConfig metadataStoreConf
                     .sessionTimeoutMs(metadataStoreConfig.getSessionTimeoutMillis())
                     .watchers(Collections.singleton(event -> {
                         if (sessionWatcher != null) {
-                            sessionWatcher.ifPresent(sw -> sw.process(event));
+                            sessionWatcher.ifPresent(sw -> executor.execute(() -> sw.process(event)));
                         }
                     }))
                     .build();