Fix ValidatorRecurringEnrollment test to account for FullNode

Previously, we were using 'clients', which means we would try to enroll full nodes,
and timeout when our (empty) enrollment was rejected.
The assert makes sure we get a valid enrollment back, and the new function conveniently
filters out full nodes and might be useful for others tests.

source/agora/test/Base.d

@@ -586,6 +586,13 @@ public class TestAPIManager
         return this.nodes.map!(np => np.client);
     }
 
+    /// Convenience function to get a range of all nodes instantiated as validators
+    public auto validators ()
+    {
+        // This is a crude way to get validators, but it works
+        return this.nodes.filter!(n => n.address.startsWith("Validator-")).map!(np => np.client);
+    }
+
     /// Registry holding the nodes
     protected AnyRegistry registry;
 

source/agora/test/ValidatorRecurringEnrollment.d

@@ -319,10 +319,11 @@ unittest
     network.generateBlocks(Height(GenesisValidatorCycle - 1));
 
     // set the recurring enrollment option to true and check in enrollment pools
-    network.clients.each!((node)
+    network.validators.each!((node)
     {
         Enrollment enroll = node.setRecurringEnrollment(true);
-        network.clients.each!(n =>
+        assert(enroll !is Enrollment.init);
+        network.validators.each!(n =>
             retryFor(n.getEnrollment(enroll.utxo_key) == enroll, 5.seconds));
     });
     network.generateBlocks(Height(GenesisValidatorCycle));