Support validate JSON file in onos-netcfg

Validate network configuration is JSON format before POST

Change-Id: I6538bba27252c2c06f387804dabe15542988bfa1
diff --git a/tools/test/bin/onos-netcfg b/tools/test/bin/onos-netcfg
index 6f49052..1cad92d 100755
--- a/tools/test/bin/onos-netcfg
+++ b/tools/test/bin/onos-netcfg
@@ -17,6 +17,11 @@
 method="POST"
 [ $file == "delete" ] && method="DELETE"
 
+# Validate JSON
+if [ $method == "POST" ]; then
+    cat $file | python -m json.tool >> /dev/null || echo "Not valid JSON File"; exit 1
+fi
+
 curl $fail -sSL --user $ONOS_WEB_USER:$ONOS_WEB_PASS \
     -X $method -H 'Content-Type:application/json' \
     http://$node:8181/onos/v1/network/configuration/${url} -d@$file