Update ping pong charm

Signed-off-by: Philip Joseph <philip.joseph@riftio.com>
diff --git a/Makefile b/Makefile
index 62e395f..bf2b4c9 100644
--- a/Makefile
+++ b/Makefile
@@ -17,7 +17,7 @@
 
 BUILD_DIR = .
 
-CHARMS:= vpe-router vyos-proxy
+CHARMS:= vpe-router vyos-proxy pingpong
 CHARM_SRC_DIR := layers
 CHARM_BUILD_DIR := $(BUILD_DIR)/builds