Use lower bound wildcard for API to be more flexible

Change-Id: Ia6bcec5afb2e872b55bae4bbd9139ad35ce01284
diff --git a/core/net/src/test/java/org/onosproject/net/intent/impl/compiler/MockResourceService.java b/core/net/src/test/java/org/onosproject/net/intent/impl/compiler/MockResourceService.java
index 4083f5b..b3ad768 100644
--- a/core/net/src/test/java/org/onosproject/net/intent/impl/compiler/MockResourceService.java
+++ b/core/net/src/test/java/org/onosproject/net/intent/impl/compiler/MockResourceService.java
@@ -44,7 +44,7 @@
     private final Map<Resource, ResourceConsumer> assignment = new HashMap<>();
 
     @Override
-    public List<ResourceAllocation> allocate(ResourceConsumer consumer, List<Resource> resources) {
+    public List<ResourceAllocation> allocate(ResourceConsumer consumer, List<? extends Resource> resources) {
         assignment.putAll(
                 resources.stream().collect(Collectors.toMap(x -> x, x -> consumer))
         );