A malicious Vhost-user master could send in loop hand-crafted
vhost-user messages containing more file descriptors the
vhost-user slave expects. Doing so causes the application using
the vhost-user library to run out of FDs.
This issue has been assigned CVE-2019-14818
Fixes: 8f972312b8f4 ("vhost: support vhost-user")
Signed-off-by: Maxime Coquelin <maxime.coquelin@redhat.com>