v2v: adding os support version for v2v

as well as fixing for broken test in el6.
el6 does not support etree syntax that is use to parse xml in v2v as
well as virt-v2v import from vmdk (libvirt image) is not supported in
el6.

Change-Id: I99a343a9634a90502feff46caed2c05b6af93ad5
Signed-off-by: Shahar Havivi <shaharh@redhat.com>
Reviewed-on: http://gerrit.ovirt.org/36388
Tested-by: Shahar Havivi <shavivi@redhat.com>
Reviewed-by: Nir Soffer <nsoffer@redhat.com>
Reviewed-by: Dan Kenigsberg <danken@redhat.com>