Minor improvements

- Fix typo
- Remove unnecessary warnings
    - Ignore dhcp config register/unregister event
    - Ignore interface IP update when there is no host discovered on that interface

Change-Id: I530fe36eb063ac8b3397c86e888c0a6c2ab8984b
diff --git a/apps/dhcprelay/src/main/java/org/onosproject/dhcprelay/DhcpRelayManager.java b/apps/dhcprelay/src/main/java/org/onosproject/dhcprelay/DhcpRelayManager.java
index 39123ac..cd4e3b5 100644
--- a/apps/dhcprelay/src/main/java/org/onosproject/dhcprelay/DhcpRelayManager.java
+++ b/apps/dhcprelay/src/main/java/org/onosproject/dhcprelay/DhcpRelayManager.java
@@ -596,6 +596,9 @@
                         log.info("{} removed", config.getClass().getSimpleName());
                     });
                     break;
+                case CONFIG_REGISTERED:
+                case CONFIG_UNREGISTERED:
+                    break;
                 default:
                     log.warn("Unsupported event type {}", event.type());
                     break;