Updated openstack/openstack
Project: openstack/tempest  3867621edcbe5f849361d83c7ff8f0a1d6ac26eb

Create subnet without gateway and explicit IP ver

Now it's impossible to create subnet without gateway in network
tests. This patch allows you to set gateway explicitly to None.
Backward compatibility is supported: by default it creates
subnet with default gateway as before. Also it adds possibility
to create subnet with specific IP version when you need to create
two subnets in one tenant of different IP version ("dual-stack").
Fixed attributes test for new requirements and added 2 anothers.

Change-Id: I7aca5e07be436f20cba90339785b46182d97fead