Don't scan gerrit_index.config for current version when no Lucene

With the index engine is not Lucene don't scan `gerrit_index.config` for
the newest version as index checking is not supported anyway. Apply the
same logic for `onSuccess` so that handler is not performing empty
updates. To be reviewed when issue 316743624 gets implemented.

Change-Id: I1f7b050b7f58cdbe35013038f45ec4195a669a8a

src/main/java/com/googlesource/gerrit/plugins/healthcheck/check/ChangesIndexHealthCheck.java

diff --git a/src/main/java/com/googlesource/gerrit/plugins/healthcheck/check/ChangesIndexHealthCheck.java b/src/main/java/com/googlesource/gerrit/plugins/healthcheck/check/ChangesIndexHealthCheck.java
index bd16b7b..fada9aa 100644
--- a/src/main/java/com/googlesource/gerrit/plugins/healthcheck/check/ChangesIndexHealthCheck.java
+++ b/src/main/java/com/googlesource/gerrit/plugins/healthcheck/check/ChangesIndexHealthCheck.java
@@ -74,7 +74,7 @@
 
   @Override
   public void onSuccess(String name, int oldVersion, int newVersion) {
-    if (!name.equals("changes") || oldVersion == newVersion) {
+    if (!isLuceneIndex || !name.equals("changes") || oldVersion == newVersion) {
       return;
     }
 
@@ -106,6 +106,10 @@
   }
 
   private Optional<ChangesIndexLockFiles> getChangesIndexLockFiles(Path indexDir) {
+    if (!isLuceneIndex) {
+      Optional.empty();
+    }
+
     FileBasedConfig cfg =
         new FileBasedConfig(indexDir.resolve("gerrit_index.config").toFile(), FS.detect());
     try {