You need to create a real integration test server.
I wrote something about this here: http://david.pilato.fr/blog/2016/10/18/elasticsearch-real-integration-tests-updated-for-ga/
A bit complicated but at least really realistic.
May be download the artifact with http://www.mojohaus.org/wagon-maven-plugin/ like:
<plugin>
<groupId>org.codehaus.mojo</groupId>
<artifactId>wagon-maven-plugin</artifactId>
<version>1.0</version>
<executions>
<execution>
<id>download-ingest-attachment</id>
<phase>pre-integration-test</phase>
<goals>
<goal>download-single</goal>
</goals>
<configuration>
<url>https://artifacts.elastic.co</url>
<fromFile>downloads/elasticsearch-plugins/ingest-attachment/ingest-attachment-5.1.2.zip</fromFile>
<toDir>${project.build.directory}/es-plugins</toDir>
</configuration>
</execution>
</executions>
</plugin>