It was supported on RDO Juno, verify on RDO Kilo
https://ask.openstack.org/en/question...
Verified on RDO Kilo CentOS 7.1

[root@ServerCentOS71 ~]# yum install openswan openstack-neutron-vpn-agent
Loaded plugins: fastestmirror, langpacks
base                                                                              | 3.6 kB  00:00:00     
epel/x86_64/metalink                                                              |  25 kB  00:00:00     
epel                                                                              | 4.4 kB  00:00:00     
extras                                                                            | 3.4 kB  00:00:00     
openstack-kilo                                                                    | 2.9 kB  00:00:00     
updates                                                                           | 3.4 kB  00:00:00     
(1/2): epel/x86_64/primary_db                                                     | 3.7 MB  00:00:01     
(2/2): openstack-kilo/primary_db                                                  | 372 kB  00:00:02     
(1/2): epel/x86_64/updateinfo                                                     | 441 kB  00:00:00     
(2/2): epel/x86_64/pkgtags                                                        | 1.6 MB  00:00:00     
Loading mirror speeds from cached hostfile
 * base: mirror.yandex.ru
 * epel: mirror.yandex.ru
 * extras: mirror.yandex.ru
 * updates: mirror.yandex.ru
Package libreswan-3.12-10.1.el7_1.x86_64 already installed and latest version
Resolving Dependencies
--> Running transaction check
---> Package openstack-neutron-vpnaas.noarch 0:2015.1.0-3.el7 will be installed
--> Processing Dependency: python-neutron-vpnaas = 2015.1.0-3.el7 for package: openstack-neutron-vpnaas-2015.1.0-3.el7.noarch
--> Running transaction check
---> Package python-neutron-vpnaas.noarch 0:2015.1.0-3.el7 will be installed
--> Finished Dependency Resolution

Dependencies Resolved

=========================================================================================================
 Package                           Arch            Version                 Repository               Size
=========================================================================================================
Installing:
 openstack-neutron-vpnaas          noarch          2015.1.0-3.el7          openstack-kilo           15 k
Installing for dependencies:
 python-neutron-vpnaas             noarch          2015.1.0-3.el7          openstack-kilo          111 k

Transaction Summary
=========================================================================================================
Install  1 Package (+1 Dependent package)

Total download size: 126 k
Installed size: 467 k
Is this ok [y/d/N]: y
Downloading packages:
(1/2): openstack-neutron-vpnaas-2015.1.0-3.el7.noarch.rpm                         |  15 kB  00:00:01     
(2/2): python-neutron-vpnaas-2015.1.0-3.el7.noarch.rpm                            | 111 kB  00:00:02     
---------------------------------------------------------------------------------------------------------
Total                                                                     53 kB/s | 126 kB  00:00:02     
Running transaction check
Running transaction test
Transaction test succeeded
Running transaction
  Installing : python-neutron-vpnaas-2015.1.0-3.el7.noarch                                           1/2 
  Installing : openstack-neutron-vpnaas-2015.1.0-3.el7.noarch                                        2/2 
  Verifying  : python-neutron-vpnaas-2015.1.0-3.el7.noarch                                           1/2 
  Verifying  : openstack-neutron-vpnaas-2015.1.0-3.el7.noarch                                        2/2 

Installed:
  openstack-neutron-vpnaas.noarch 0:2015.1.0-3.el7                                                       

Dependency Installed:
  python-neutron-vpnaas.noarch 0:2015.1.0-3.el7                                                          

Complete!

Try to follow https://gist.github.com/cloudnull/885... on RDO Kilo