IndexTs: Fix log formatting

Add missing argument to log formatting, and use Logger's built-in
String formatting.

Change-Id: Ic5d9431b9c349e01cac3eb5c06ac096e63dfd561
diff --git a/src/main/java/com/ericsson/gerrit/plugins/highavailability/autoreindex/IndexTs.java b/src/main/java/com/ericsson/gerrit/plugins/highavailability/autoreindex/IndexTs.java
index 0466409..4c3eafa 100644
--- a/src/main/java/com/ericsson/gerrit/plugins/highavailability/autoreindex/IndexTs.java
+++ b/src/main/java/com/ericsson/gerrit/plugins/highavailability/autoreindex/IndexTs.java
@@ -68,7 +68,7 @@
         try {
           Files.write(indexTsFile, latestTs.format(formatter).getBytes(StandardCharsets.UTF_8));
         } catch (IOException e) {
-          log.error("Unable to update last timestamp for index " + index, e);
+          log.error("Unable to update last timestamp for index {}", index, e);
         }
       }
     }
@@ -100,7 +100,7 @@
           IndexName.CHANGE,
           change == null ? LocalDateTime.now() : change.getLastUpdatedOn().toLocalDateTime());
     } catch (OrmException e) {
-      log.warn("Unable to update the latest TS for change {}", e);
+      log.warn("Unable to update the latest TS for change {}", id, e);
     }
   }