This patch stops a socket driver from using copyfd(2) to copy in a
file descriptor that is a reference to a socket owned by that socket
driver, returning EDEADLK instead. In effect, this will stop deadlock
and resource exhaustion issues with UDS once it has been converted to
a socket driver. See the comment in the patch for details.
Change-Id: I5728a405eabda207725618231a6ff7be2d517146