adt-xenlvm-setup assumes /etc/lsb-version which is only in ubuntu

[timo.lindfors@iki.fi (Timo Juhani Lindfors)]

Hi,

$ adt-xenlvm-setup 
considering which distro to use ... xenlvm: adt-xenlvm-setup: error: no /etc/lsb-version, config must specify adt_distro

can't we just use `lsb_release --short --codename` instead?

-Timo