Log stack trace when an error occur while deleting event

This will help figuring out root cause of failure to delete event file.

Change-Id: I2f9774c3daf19a04f6b04414ba8145c99bb6e0fe
(cherry picked from commit b62f006b1350180de0af02c82fb18fb290a2548f)

src/main/java/com/googlesource/gerrit/plugins/replication/EventsStorage.java

diff --git a/src/main/java/com/googlesource/gerrit/plugins/replication/EventsStorage.java b/src/main/java/com/googlesource/gerrit/plugins/replication/EventsStorage.java
index 36d9ce0..c567876 100644
--- a/src/main/java/com/googlesource/gerrit/plugins/replication/EventsStorage.java
+++ b/src/main/java/com/googlesource/gerrit/plugins/replication/EventsStorage.java
@@ -75,7 +75,7 @@
       try {
         Files.delete(refUpdates().resolve(eventKey));
       } catch (IOException e) {
-        log.error("Error while deleting event {}", eventKey);
+        log.error("Error while deleting event {}", eventKey, e);
       }
     }
   }