test: Use the 'withTag' helper to get DockerImageName

This results in less duplication when we have multiple images with the
same name and different tags.

Change-Id: I705f927faa4f698fa4f96e8039f08bac70965c29

src/test/java/com/google/gerrit/elasticsearch/ElasticContainer.java

diff --git a/src/test/java/com/google/gerrit/elasticsearch/ElasticContainer.java b/src/test/java/com/google/gerrit/elasticsearch/ElasticContainer.java
index 86b1bac..76f425c 100644
--- a/src/test/java/com/google/gerrit/elasticsearch/ElasticContainer.java
+++ b/src/test/java/com/google/gerrit/elasticsearch/ElasticContainer.java
@@ -39,16 +39,17 @@
     return container;
   }
 
-  private static String getImageName(ElasticVersion version) {
+  private static DockerImageName getImageName(ElasticVersion version) {
+    DockerImageName image = DockerImageName.parse("docker.elastic.co/elasticsearch/elasticsearch");
     switch (version) {
       case V7_16:
-        return "docker.elastic.co/elasticsearch/elasticsearch:7.16.2";
+        return image.withTag("7.16.2");
     }
     throw new IllegalStateException("No tests for version: " + version.name());
   }
 
   private ElasticContainer(ElasticVersion version) {
-    super(DockerImageName.parse(getImageName(version)));
+    super(getImageName(version));
   }
 
   @Override