engine: resources: Receive keys should match mcl, not golang

The capitalization of these keys was wrong and they weren't getting
seen. Add a test as well.

engine/resources/print.go

@@ -85,9 +85,9 @@ func (obj *PrintRes) Watch(ctx context.Context) error {
 // CheckApply method for Print resource. Does nothing, returns happy!
 func (obj *PrintRes) CheckApply(ctx context.Context, apply bool) (bool, error) {
 	obj.init.Logf("CheckApply: %t", apply)
-	if val, exists := obj.init.Recv()["Msg"]; exists && val.Changed {
+	if val, exists := obj.init.Recv()["msg"]; exists && val.Changed {
 		// if we received on Msg, and it changed, log message
-		obj.init.Logf("CheckApply: Received `Msg` of: %s", obj.Msg)
+		obj.init.Logf("CheckApply: Received `msg` of: %s", obj.Msg)
 	}
 
 	var refresh = obj.init.Refresh()