Simplify Init for Elasticsearch

Perform reindex operation for all indexes on init for elasticsearch
index. This change allows for starting an elasticsearch index with only
the init command, similar to a Lucene index.

Remove reindex operation on ElasticReindexIT, since with this change
performing a reindex manually is no longer needed.

Test plan: Run InitIT, ElasticReindexIT and ReindexIT.

This change is Index type agnostic and affects both Lucene and
Elasticsearch. If any of these index types used by a Gerrit instance do
not "exist", they will be reindexed. However, it is mostly focused
towards Elasticsearch which usually requires a manual reindex before
initializing a Gerrit site.

Bug: Issue 12909
Feature: Issue 12704
Change-Id: If7741771e25a6063c5116ab2bce39fbe0e0ea93b
(cherry-picked from 90b130e4f7129796954f73065494da9825f62169)
diff --git a/javatests/com/google/gerrit/acceptance/pgm/ElasticReindexIT.java b/javatests/com/google/gerrit/acceptance/pgm/ElasticReindexIT.java
index 38b7e0e..cf349ab 100644
--- a/javatests/com/google/gerrit/acceptance/pgm/ElasticReindexIT.java
+++ b/javatests/com/google/gerrit/acceptance/pgm/ElasticReindexIT.java
@@ -21,7 +21,6 @@
 import com.google.gerrit.testing.ConfigSuite;
 import com.google.inject.Injector;
 import org.eclipse.jgit.lib.Config;
-import org.junit.Before;
 
 public class ElasticReindexIT extends AbstractReindexTests {
 
@@ -39,10 +38,4 @@
   public void configureIndex(Injector injector) {
     createAllIndexes(injector);
   }
-
-  @Before
-  public void reindexFirstSinceElastic() throws Exception {
-    assertServerStartupFails();
-    runGerrit("reindex", "-d", sitePaths.site_path.toString(), "--show-stack-trace");
-  }
 }