Actually I am thinking about if we should not use vm.create() in the tests scripts at all. It may cause the problems that the vm we get from env is not the same that we create in our test. So some very strange error may happen because of this in a test loop between two cases.

As we use env to pass vm object between tests. We should pay more attention when we use it. So a extra function like env_process.preprocess_vm() is a good choice so far.

Change the start_vm to yes when you want to start a vm is easier to accept than a wired error in following tests.