virt-libvirt: Unify virsh function 'name' parameters

* Renamed vm_name -> name
* Updated docstrings
* Clarified several other parameters.

Signed-off-by: Li Yang <liyang.fnst@cn.fujitsu.com>
Merge pull request #685 from liyangfnst/vm_name

virt-libvirt: Unify virsh function 'name' parameters

* Renamed vm_name -> name
* Updated docstrings
* Clarified several other parameters.