Fixing javadoc groups.

Change-Id: If3dc0f78e7470c9f0a6881b6f22beda00e1d3180
diff --git a/docs/external-excludes b/docs/external-excludes
index 9c1824f..34329f1 100644
--- a/docs/external-excludes
+++ b/docs/external-excludes
@@ -9,6 +9,7 @@
 org.onosproject.rest
 org.onosproject.cli*
 org.onosproject.tvue
+org.onosproject.dhcp
 org.onosproject.foo
 org.onosproject.mobility
 org.onosproject.proxyarp