RFE: add LSM/SELinux access controls for AF_VSOCK sockets

[pcmoore]

AF_VSOCK is a communications channel between a VM and the hypervisor that was created by VMware and has since been adopted by other hypervisors.

• http://www.phoronix.com/scan.php?page=news_item&px=MTI3MTE
• http://wiki.qemu.org/Features/VirtioVsock

[pcmoore]

We have basic socket permissions via the "vsock_socket" object class, and the lack of problem reports or feature requests leads me to believe that it is sufficient for now.