[SPARK-25954][SS][FOLLOWUP][TEST-MAVEN] Add Zookeeper 3.4.7 test dependency to Kafka modules

## What changes were proposed in this pull request?

This is a followup of apache#23099 . After upgrading to Kafka 2.1.0, maven test fails due to Zookeeper test dependency while sbt test succeeds.

- [sbt test on master branch](https://amplab.cs.berkeley.edu/jenkins/view/Spark%20QA%20Test%20(Dashboard)/job/spark-master-test-sbt-hadoop-2.7/5203/)
- [maven test on master branch](https://amplab.cs.berkeley.edu/jenkins/view/Spark%20QA%20Test%20(Dashboard)/job/spark-master-test-maven-hadoop-2.7/5653/)

The root cause is that the embedded Kafka server is using [Zookeepr 3.4.7 API](https://zookeeper.apache.org/doc/r3.4.7/api/org/apache/zookeeper/AsyncCallback.MultiCallback.html
) while Apache Spark provides Zookeeper 3.4.6. This PR adds a test dependency.

```
KafkaMicroBatchV2SourceSuite:
*** RUN ABORTED ***
...
org.apache.spark.sql.kafka010.KafkaTestUtils.setupEmbeddedKafkaServer(KafkaTestUtils.scala:123)
  ...
  Cause: java.lang.ClassNotFoundException: org.apache.zookeeper.AsyncCallback$MultiCallback
  at java.net.URLClassLoader.findClass(URLClassLoader.java:381)
  at java.lang.ClassLoader.loadClass(ClassLoader.java:424)
  at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:331)
  at java.lang.ClassLoader.loadClass(ClassLoader.java:357)
  at kafka.zk.KafkaZkClient$.apply(KafkaZkClient.scala:1693)
  at kafka.server.KafkaServer.createZkClient$1(KafkaServer.scala:348)
  at kafka.server.KafkaServer.initZkClient(KafkaServer.scala:372)
  at kafka.server.KafkaServer.startup(KafkaServer.scala:202)
  at org.apache.spark.sql.kafka010.KafkaTestUtils.$anonfun$setupEmbeddedKafkaServer$2(KafkaTestUtils.scala:120)
  at org.apache.spark.sql.kafka010.KafkaTestUtils.$anonfun$setupEmbeddedKafkaServer$2$adapted(KafkaTestUtils.scala:116)
  ...
```

## How was this patch tested?

Pass the maven Jenkins test.

Closes apache#23119 from dongjoon-hyun/SPARK-25954-2.

Authored-by: Dongjoon Hyun <[email protected]>
Signed-off-by: Dongjoon Hyun <[email protected]>

Author: dongjoon-hyun

external/kafka-0-10-sql/pom.xml

@@ -89,6 +89,13 @@
         </exclusion>
       </exclusions>
     </dependency>
+    <!-- Kafka embedded server uses Zookeeper 3.4.7 API -->
+    <dependency>
+      <groupId>org.apache.zookeeper</groupId>
+      <artifactId>zookeeper</artifactId>
+      <version>3.4.7</version>
+      <scope>test</scope>
+    </dependency>
     <dependency>
       <groupId>net.sf.jopt-simple</groupId>
       <artifactId>jopt-simple</artifactId>

external/kafka-0-10/pom.xml

@@ -74,6 +74,13 @@
         </exclusion>
       </exclusions>
     </dependency>
+    <!-- Kafka embedded server uses Zookeeper 3.4.7 API -->
+    <dependency>
+      <groupId>org.apache.zookeeper</groupId>
+      <artifactId>zookeeper</artifactId>
+      <version>3.4.7</version>
+      <scope>test</scope>
+    </dependency>
     <dependency>
       <groupId>net.sf.jopt-simple</groupId>
       <artifactId>jopt-simple</artifactId>