KAFKA-6302: Improve AdmintClient JavaDocs

Reviewers: Colin P. McCabe <[email protected]>, Ismael Juma <[email protected]>

Closes apache#4332

clients/src/main/java/org/apache/kafka/clients/admin/AdminClient.java

@@ -105,7 +105,7 @@ public CreateTopicsResult createTopics(Collection<NewTopic> newTopics) {
      *
      * This operation is not transactional so it may succeed for some topics while fail for others.
      *
-     * It may take several seconds after this method returns
+     * It may take several seconds after {@code CreateTopicsResult} returns
      * success for all the brokers to become aware that the topics have been created.
      * During this time, {@link AdminClient#listTopics()} and {@link AdminClient#describeTopics(Collection)}
      * may not return information about the new topics.
@@ -138,7 +138,7 @@ public DeleteTopicsResult deleteTopics(Collection<String> topics) {
      *
      * This operation is not transactional so it may succeed for some topics while fail for others.
      *
-     * It may take several seconds after AdminClient#deleteTopics returns
+     * It may take several seconds after the {@code DeleteTopicsResult} returns
      * success for all the brokers to become aware that the topics are gone.
      * During this time, AdminClient#listTopics and AdminClient#describeTopics
      * may continue to return information about the deleted topics.