rhel: provide our own SELinux custom policy package

rhel: provide our own SELinux custom policy package

CentOS, RHEL and Fedora distributions ship with their own Open vSwitch
SELinux policy that is too strict and prevents Open vSwitch to work
normally out of the box.

As a solution, this patch introduces a new package which will "loosen"
up "openvswitch_t" SELinux domain so that Open vSwitch could operate
normally.

Intended use-cases of this package are:
1. to allow users to install newer Open vSwitch on already released Fedora,
RHEL and CentOS distributions where the default Open vSwitch SELinux policy
that shipped with the corresponding Linux distribution is not up to date
and did not anticipate that a newer Open vSwitch version might need to
invoke new system calls or need to access certain system resources that
it did not before; And
2. to provide alternative means through which Open vSwitch developers
can proactively fix SELinux related policy issues without waiting for
corresponding Linux distribution maintainers to update their central
Open vSwitch SELinux policy.

This patch was tested on Fedora 23 and CentOS 7. I verified that now
on Fedora 23 Open vSwitch can create a NetLink socket; and that I did
not see following error messages:

vlog|INFO|opened log file /var/log/openvswitch/ovs-vswitchd.log
ovs_numa|INFO|Discovered 2 CPU cores on NUMA node 0
ovs_numa|INFO|Discovered 1 NUMA nodes and 2 CPU cores
reconnect|INFO|unix:/var/run/openvswitch/db.sock: connecting...
reconnect|INFO|unix:/var/run/openvswitch/db.sock: connected
netlink_socket|ERR|fcntl: Permission denied
dpif_netlink|ERR|Generic Netlink family 'ovs_datapath' does not exist.
                 The Open vSwitch kernel module is p robably not loaded.
dpif|WARN|failed to enumerate system datapaths: Permission denied
dpif|WARN|failed to create datapath ovs-system: Permission denied

I did not test all Open vSwitch features so there still could be some
OVS configuration that would get "Permission denied" errors.

Since, Open vSwitch daemons on Ubuntu 15.10 by default run under "unconfined"
SELinux domain, then there is no need to create a similar debian package
for Ubuntu, because it works on default Ubuntu installation.

Signed-off-by: Ansis Atteka <aatteka@nicira.com>
Acked-by: Flavio Leitner <fbl@sysclose.com>