vhost: fix potential memory space leak

vhost: fix potential memory space leak

A malicious container which has direct access to the vhost-user socket
can keep sending VHOST_USER_GET_INFLIGHT_FD messages which may cause
leaking resources until resulting a DOS. Fix it by unmapping the
dev->inflight_info->addr before assigning new mapped addr to it.

CVE-2020-10726
Fixes: d87f1a1cb7b6 ("vhost: support inflight info sharing")
Cc: stable@dpdk.org
Signed-off-by: Xiaolong Ye <xiaolong.ye@intel.com>
Reviewed-by: Maxime Coquelin <maxime.coquelin@redhat.com>