Fix getRefsByPrefix usage

Ie1b9ebd194a4ca2542d9aaf5c59c71dfbb361676 removed usage of the
deprecated getRefs(PREFIX) API, but missed that the returned key was
being used and the key had the prefix removed. Get ls-batches working
correctly again by stripping the prefix from the returned Ref.

Change-Id: I86784fdeb3a39e6d4ad44a75dcb57dd14c91db18

src/main/java/com/googlesource/gerrit/plugins/batch/BatchStore.java

diff --git a/src/main/java/com/googlesource/gerrit/plugins/batch/BatchStore.java b/src/main/java/com/googlesource/gerrit/plugins/batch/BatchStore.java
index 9c0db7b..d582af4 100644
--- a/src/main/java/com/googlesource/gerrit/plugins/batch/BatchStore.java
+++ b/src/main/java/com/googlesource/gerrit/plugins/batch/BatchStore.java
@@ -62,8 +62,9 @@
     List<Batch> batches = new ArrayList<>();
     try (Repository repo = repoManager.openRepository(project)) {
       for (Ref ref : repo.getRefDatabase().getRefsByPrefix(BATCHES_REF)) {
+        String id = ref.getName().substring(BATCHES_REF.length());
         try {
-          batches.add((includeBatchInfo == true) ? read(ref.getName()) : new Batch(ref.getName()));
+          batches.add((includeBatchInfo == true) ? read(id) : new Batch(id));
         } catch (NoSuchBatchException e) {
           continue;
         }