Construct GraphDescription with online/active Device/Link only

Change-Id: I9312c0c8ae190bf0200bd040823b6f7a3e7a15e1
diff --git a/core/api/src/test/java/org/onlab/onos/net/device/DeviceServiceAdapter.java b/core/api/src/test/java/org/onlab/onos/net/device/DeviceServiceAdapter.java
index 6b4ed3b..3d2d74f 100644
--- a/core/api/src/test/java/org/onlab/onos/net/device/DeviceServiceAdapter.java
+++ b/core/api/src/test/java/org/onlab/onos/net/device/DeviceServiceAdapter.java
@@ -21,6 +21,9 @@
 import org.onlab.onos.net.Port;
 import org.onlab.onos.net.PortNumber;
 
+import com.google.common.base.Predicate;
+import com.google.common.collect.FluentIterable;
+
 import java.util.List;
 
 /**
@@ -38,6 +41,18 @@
     }
 
     @Override
+    public Iterable<Device> getAvailableDevices() {
+        return FluentIterable.from(getDevices())
+                .filter(new Predicate<Device>() {
+
+                    @Override
+                    public boolean apply(Device input) {
+                        return isAvailable(input.id());
+                    }
+                });
+    }
+
+    @Override
     public Device getDevice(DeviceId deviceId) {
         return null;
     }