fence_azure_arm: fix get virtual machines call

The function virtual_machines.get() has changed it's signature from:

def get(
    self,
    resource_group_name,
    expand=None,
    **kwargs
):

to:

def get(
    self,
    resource_group_name: str,
    machine_name: str,
    expand: Optional[Union[str, _models.InstanceViewTypes]] = None,
    **kwargs: Any
    ) -> _models.Machine:

Therefore, the number of positional arguments has been reduced to two:
resource_group_name and machine_name, while the expand
parameter has swift from a *positional argument* to a *keyword-only
argument*.

Signed-off-by: Javier Cano Cano <jcanocan@redhat.com>