vhost: check message header size read

vhost: check message header size read

This patch adds a check to ensure the read size of
the Vhost-user message header is not smaller than
the expected size.

In case of unexpected read size, report an error
and close file descriptors passed with the message,
if any.

Fixes: 8f972312b8f4 ("vhost: support vhost-user")
Cc: stable@dpdk.org
Reported-by: Ilja Van Sprundel <ivansprundel@ioactive.com>
Signed-off-by: Maxime Coquelin <maxime.coquelin@redhat.com>
Reviewed-by: Tiwei Bie <tiwei.bie@intel.com>