vhost: add runtime locking check in unsafe API

vhost: add runtime locking check in unsafe API

This patch adds runtime checks in unsafe Vhost async APIs,
to ensure the access lock is taken.

The detection won't work every time, as another thread
could take the lock, but it would help to detect misuse
of these unsafe API.

Signed-off-by: Maxime Coquelin <maxime.coquelin@redhat.com>
Reviewed-by: David Marchand <david.marchand@redhat.com>
Reviewed-by: Jiayu Hu <jiayu.hu@intel.com>
Reviewed-by: Chenbo Xia <chenbo.xia@intel.com>