Fix bug in validate() in BooleanConstraint

- Flip the branch condition in validate()

Change-Id: I7bafb710440513d3ccce8178c1bd6bb30ed06d4f

@@ -52,7 +52,7 @@ public abstract class BooleanConstraint implements Constraint {
     @Override
     public boolean validate(Path path, LinkResourceService resourceService) {
         for (Link link : path.links()) {
-            if (isValid(link, resourceService)) {
+            if (!isValid(link, resourceService)) {
                 return false;
             }
         }

@@ -19,7 +19,6 @@ import com.google.common.base.MoreObjects;
 import com.google.common.collect.ImmutableSet;
 import org.onlab.onos.net.DeviceId;
 import org.onlab.onos.net.Link;
-import org.onlab.onos.net.Path;
 import org.onlab.onos.net.resource.LinkResourceService;
 
 import java.util.Objects;
@@ -49,17 +48,6 @@ public class ObstacleConstraint extends BooleanConstraint {
     }
 
     @Override
-    public boolean validate(Path path, LinkResourceService resourceService) {
-        for (Link link : path.links()) {
-            if (!isValid(link, resourceService)) {
-                return false;
-            }
-        }
-
-        return true;
-    }
-
-    @Override
     public int hashCode() {
         return Objects.hash(obstacles);
     }