Evaluator: Replace ScheduledThreadPoolExecutor use with ExecutorService

Fix the loading of this plugin in a gerrit site, namely the adaptation
started with change Ib023c65cd.

Before this current change, plugin loading failed with the binding error
described in the Issue below.

Bug: Issue 12738
Change-Id: Ie4cdc8ea9e114613ce739a768d884c6e214cf053
diff --git a/src/main/java/com/ericsson/gerrit/plugins/gcconductor/evaluator/Evaluator.java b/src/main/java/com/ericsson/gerrit/plugins/gcconductor/evaluator/Evaluator.java
index 5ae7fac..eda5f96 100644
--- a/src/main/java/com/ericsson/gerrit/plugins/gcconductor/evaluator/Evaluator.java
+++ b/src/main/java/com/ericsson/gerrit/plugins/gcconductor/evaluator/Evaluator.java
@@ -31,8 +31,8 @@
 import java.util.Map;
 import java.util.Set;
 import java.util.concurrent.ConcurrentHashMap;
+import java.util.concurrent.ExecutorService;
 import java.util.concurrent.Future;
-import java.util.concurrent.ScheduledThreadPoolExecutor;
 import org.eclipse.jgit.errors.RepositoryNotFoundException;
 import org.eclipse.jgit.lib.Config;
 import org.eclipse.jgit.lib.ObjectId;
@@ -48,7 +48,7 @@
   private static final Logger log = LoggerFactory.getLogger(Evaluator.class);
   private static final ThreadLocal<String> uploadRepositoryPath = new ThreadLocal<String>() {};
 
-  private final ScheduledThreadPoolExecutor executor;
+  private final ExecutorService executor;
   private final EvaluationTask.Factory evaluationTaskFactory;
   private final GitRepositoryManager repoManager;
   private final Map<String, Long> timestamps;
@@ -59,7 +59,7 @@
 
   @Inject
   Evaluator(
-      @EvaluatorExecutor ScheduledThreadPoolExecutor executor,
+      @EvaluatorExecutor ExecutorService executor,
       EvaluationTask.Factory evaluationTaskFactory,
       GitRepositoryManager repoManager,
       EvaluatorConfig config,
diff --git a/src/test/java/com/ericsson/gerrit/plugins/gcconductor/evaluator/EvaluatorTest.java b/src/test/java/com/ericsson/gerrit/plugins/gcconductor/evaluator/EvaluatorTest.java
index 7dc403b..c51d2a8 100644
--- a/src/test/java/com/ericsson/gerrit/plugins/gcconductor/evaluator/EvaluatorTest.java
+++ b/src/test/java/com/ericsson/gerrit/plugins/gcconductor/evaluator/EvaluatorTest.java
@@ -29,7 +29,7 @@
 import java.io.File;
 import java.io.IOException;
 import java.util.concurrent.CompletableFuture;
-import java.util.concurrent.ScheduledThreadPoolExecutor;
+import java.util.concurrent.ExecutorService;
 import org.eclipse.jgit.errors.RepositoryNotFoundException;
 import org.eclipse.jgit.lib.Config;
 import org.eclipse.jgit.lib.Repository;
@@ -49,7 +49,7 @@
   @Mock private GitRepositoryManager repoManager;
   @Mock private Repository repository;
   @Mock private Repository repositoryOther;
-  @Mock private ScheduledThreadPoolExecutor executor;
+  @Mock private ExecutorService executor;
   @Mock private EvaluatorConfig config;
   @Mock private Config gerritConfig;