Add dhcpl2relay to gitignore

Change-Id: If56dfe851bfcd0463083ae5af8013322628a1a5a
diff --git a/.gitignore b/.gitignore
index ee1967b..5d073c0 100644
--- a/.gitignore
+++ b/.gitignore
@@ -50,4 +50,5 @@
 apps/carrierethernet/
 apps/sadis/
 apps/igmpproxy/
+apps/dhcpl2relay/