Make network_vlan_ranges available in GRE setups

Ensure that network_vlan_ranges can be set when
tenant_network_type=gre as well.

Resolves: bz#1006534

Change-Id: Ibc18a5b44d60a71656392079ef76f99f298e5a66
Merge "Make network_vlan_ranges available in GRE setups"