By default the openstack inventory fetches the first fixed ip
address for "ansible_host" and "ansible_ssh_host".
Due to the random sorting of addresses by OpenStack, this can either be
a ipv4 or ipv6 address, this is not desirable in some legacy setups
where Ansible runs in a ipv4 only setup,
but OpenStack is already ipv6 enabled.
To prevent this, a new option called "only_ipv4" was added,
which forces the inventory plugin to use only fixed ipv4 addresses.
Closes-Bug: #2051249
Change-Id: I3aa9868c9299705d4b0dcbf9b9cb561c0855c11c
c5d0d3ec82