Fix: Add EPIPE error handling on buffer splice

Even though this is _not_ documented in splice(2), if the fd_out is a
socket but closed on one end, splice returns a negative value and set
errno to EPIPE. The man page specifies a EBADF but I guess both are
possible (and it is according to the kernel 3.6.2 source).

So, when streaming a kernel session (using splice), if the relayd quits,
a splice on the socket returns an EPIPE.

Signed-off-by: David Goulet <dgoulet@efficios.com>