Return false when replicate already saved

Author: mcornaton

src/main/java/com/iexec/core/replicate/ReplicatesService.java

@@ -82,6 +82,7 @@ public boolean addNewReplicate(ReplicatesList replicatesList, String walletAddre
             log.info("New replicate saved [chainTaskId:{}, walletAddress:{}]", chainTaskId, walletAddress);
         } else {
             log.error("Replicate already saved [chainTaskId:{}, walletAddress:{}]", chainTaskId, walletAddress);
+            return false;
         }
 
         return true;