libvirt-machine: Don't leak volume on failed stop or delete
libvirt-machine: Don't leak volume on failed stop or delete

If domain is already stopped, attempting to stop it will fail. Put all
clean-up operations related to deletion in their own try/catch block so
failure of one doesn't mean the others wont be executed.

https://bugzilla.gnome.org/show_bug.cgi?id=682901

vbenes/gnome-boxes,vbenes/gnome-boxes