We need to close the old slave request fd if any first
before taking the new one.
Fixes: 275c3f944730 ("vhost: support slave requests channel")
Cc: stable@dpdk.org
Signed-off-by: Tiwei Bie <tiwei.bie@intel.com>
Reviewed-by: Maxime Coquelin <maxime.coquelin@redhat.com>