Regression test portability: mknod

Linux mknod(2) is able to create fifo and named sockets. NetBSD and
FreeBSD use mkfifo(2) and socket(2)/bind(2) for that.

BUG: 764655
Change-Id: I1d3969e3fcb6afdbd184c28bd268ffa2da7ae202
Signed-off-by: Emmanuel Dreyfus <manu@netbsd.org>
Reviewed-on: http://review.gluster.org/8433
Tested-by: Gluster Build System <jenkins@build.gluster.com>
Reviewed-by: Vijay Bellur <vbellur@redhat.com>