Add SELinux policy for Horizon

httpd, due to Horizon,  needs SELinux policy to allow it to connect to
the various ports for the OpenStack services. We can add this policy by
setting the SELinux boolean httpd_can_network_connect.

Change-Id: I663e543ddb1738c5e2de40b37d5a0e697762feb4
Closes-Bug: 1361630
Merge "Add SELinux policy for Horizon"