Use valid uuid when creating a network
Use valid uuid when creating a network

Recent changes in neutron (I20b24ee57c521b1c68977c2ff7ae56b56875dd64)
ensures uuid db fields are being validated, this breaks l2gw unittest on
depended repos (e.g - vmware_nsx), as there are occurence of non-valid
network-id uuid field in test_l2gw:L2GWTestCase._get_nw_data.

Change-Id: If2b41b7274e381723a1b178299aaaf63505a80d5

openstack/networking-l2gw,openstack/networking-l2gw