parallels: create VMs in the default place
    
    Each VM consists of a set of files in PCS: config, hard
    disk images, log file, memory dump. All these files are stored
    in a per-vm directory. When we create a new VM, we can ether specify
    path to the VM or create the VM in a default path
    (<default path>/<vm name>.pvm). This default path can be configured
    with command
    prlsrvctl user set --def-vm-home <path> command.
    
    Currenty parallels driver creates VM in the same place, where first
    hard disk is located. Let's change this logic and create VMs in
    the default path. It will be much clearer and allow us to create
    VMs without hard disks.
    
    Signed-off-by: Dmitry Guryanov <dguryanov@parallels.com>