Fix cache invalidation of path_owners_entries

Change-Id: If6039a23b33c2900434dce82bc1fc19bcab92b92
diff --git a/owners-common/src/main/java/com/googlesource/gerrit/owners/common/PathOwnersEntriesCacheImpl.java b/owners-common/src/main/java/com/googlesource/gerrit/owners/common/PathOwnersEntriesCacheImpl.java
index 3af7a58..c882414 100644
--- a/owners-common/src/main/java/com/googlesource/gerrit/owners/common/PathOwnersEntriesCacheImpl.java
+++ b/owners-common/src/main/java/com/googlesource/gerrit/owners/common/PathOwnersEntriesCacheImpl.java
@@ -20,6 +20,7 @@
 import com.google.common.cache.LoadingCache;
 import com.google.common.collect.HashMultimap;
 import com.google.common.collect.Multimap;
+import com.google.gerrit.entities.RefNames;
 import com.google.inject.Inject;
 import com.google.inject.Singleton;
 import com.google.inject.name.Named;
@@ -88,6 +89,6 @@
   }
 
   private String indexKey(String project, String branch) {
-    return new StringBuilder(project).append('@').append(branch).toString();
+    return new StringBuilder(project).append('@').append(RefNames.fullName(branch)).toString();
   }
 }