CA-151613: Pass -priv flag to qemu when doing PCI passthrough

This was originally removed on the xs64bit branch as CA-133523, but the
removal was reverted.

Signed-off-by: John Else <john.else@citrix.com>
Merge pull request #155 from johnelse/pass-priv-to-qemu

CA-151613: Pass -priv flag to qemu when doing PCI passthrough