Don't be too strict for vlan_ranges

VLAN range can be also in format of physical network or with only
single ID. This patch makes those values pass the validation

For more info please check https://bugzilla.redhat.com/show_bug.cgi?id=1066549

Change-Id: I054fbd45ac2228a3a579c08cdd617d970abcaddf
(cherry picked from commit 8fd57075d13e7c4e84e66378e2490eb02f3a00c1)