SLING-5321 : syncTokenService dependency should be mandatory, not optional, to avoid inconsistency between availability of the syncTokenService in a cluster

git-svn-id: https://svn.apache.org/repos/asf/sling/trunk@1715827 13f79535-47bb-0310-9956-ffa450edef68
diff --git a/src/main/java/org/apache/sling/discovery/impl/DiscoveryServiceImpl.java b/src/main/java/org/apache/sling/discovery/impl/DiscoveryServiceImpl.java
index 6d3ca41..3fd2f15 100644
--- a/src/main/java/org/apache/sling/discovery/impl/DiscoveryServiceImpl.java
+++ b/src/main/java/org/apache/sling/discovery/impl/DiscoveryServiceImpl.java
@@ -152,7 +152,7 @@
     @Reference
     private Config config;
     
-    @Reference(cardinality = ReferenceCardinality.OPTIONAL_UNARY)
+    @Reference
     private SyncTokenService syncTokenService;
 
     /** the slingId of the local instance **/