Update Vagrantfile to include CentOS7
Update Vagrantfile to include CentOS7

Change-Id: I5c8a3b64903bfac657e445eeb5895bda35f33b50

bunchc/openstack-ansible,BjoernT/os-ansible-deployment,os-cloud/os-ansible-deployment,robb-romans/openstack-ansible,cfarquhar/openstack-ansible,cloudnull/os-ansible-deployment,BjoernT/os-ansible-deployment,robb-romans/openstack-ansible,os-cloud/os-ansible-deployment,yanyao/openstack-ansible,BjoernT/os-ansible-deployment,cfarquhar/openstack-ansible,openstack/openstack-ansible,openstack/openstack-ansible,stackforge/os-ansible-deployment,bunchc/openstack-ansible,BjoernT/openstack-ansible,yanyao/openstack-ansible,BjoernT/openstack-ansible,stackforge/os-ansible-deployment,cloudnull/os-ansible-deployment