Test_common.make_pif: correct default value of iPv6 param to empty list
Test_common.make_pif: correct default value of iPv6 param to empty list

Signed-off-by: Gabor Igloi <7535f5501fd71876c93d896691e178fd3a11cfbb@citrix.com>

euanh/xen-api,srowe/xen-api,srowe/xen-api,srowe/xen-api,srowe/xen-api,srowe/xen-api,euanh/xen-api,euanh/xen-api,euanh/xen-api,euanh/xen-api,euanh/xen-api