Check if virtual machine file system has been mounted during "tycoon host create_account"

[dana]

"tycoon host create_account" command returns when the virtual machine has been booted. It doesn't test if the file system has been mounted or not.

It is a usability problem (we can't interact with the virtual machine and we don't know when it will be ready) and could be a security problem (the account creation and the virtual machine boot should be, both, an atomic operation).

The "tycoon host create_account" command should wait till the virtual machine be ready and, after that, return.