SPARK-6205 [CORE] UISeleniumSuite fails for Hadoop 2.x test with NoClassDefFoundError

Add xml-apis to core test deps to work aroudn UISeleniumSuite classpath issue

Author: Sean Owen <sowen@cloudera.com>

Closes #4933 from srowen/SPARK-6205 and squashes the following commits:

ddd4d32 [Sean Owen] Add xml-apis to core test deps to work aroudn UISeleniumSuite classpath issue

core/pom.xml

@@ -319,6 +319,12 @@
       <artifactId>selenium-java</artifactId>
       <scope>test</scope>
     </dependency>
+    <!-- Added for selenium: -->
+    <dependency>
+      <groupId>xml-apis</groupId>
+      <artifactId>xml-apis</artifactId>
+      <scope>test</scope>
+    </dependency>
     <dependency>
       <groupId>org.mockito</groupId>
       <artifactId>mockito-all</artifactId>

pom.xml

@@ -422,6 +422,13 @@
         <version>2.42.2</version>
         <scope>test</scope>
       </dependency>
+      <!-- Added for selenium only, and should match its dependent version: -->
+      <dependency>
+        <groupId>xml-apis</groupId>
+        <artifactId>xml-apis</artifactId>
+        <version>1.4.01</version>
+        <scope>test</scope>
+      </dependency>
       <dependency>
         <groupId>org.slf4j</groupId>
         <artifactId>slf4j-api</artifactId>