A simple misplaced break out of a switch results in:

  libvir: error : Failed to open file '/sys/bus/pci/devices/0000:00:54c./vendor': No such file or directory
  libvir: error : Failed to open file '/sys/bus/pci/devices/0000:00:54c./device': No such file or directory
  libvir: error : this function is not supported by the hypervisor: Failed to read product/vendor ID for 0000:00:54c.

when trying to passthrough a USB host device to qemu.

* src/security_selinux.c: fix a switch/break thinko