vhost: fix IOTLB on NUMA realloc

vhost: fix IOTLB on NUMA realloc

In case of NUMA reallocation, virtqueue's iotlb list is broken,
has its head changes but first iotlb entry in the list still points
to the previous head pointer.

Also, in case of reallocation, we want the IOTLB cache mempool to be
on the new socket.

This patch perform a full re-init of the IOTLB cache when mempool
already exists, and calls the IOTLB cache init function in case
the virtqueue is being reallocated on a new socket.

Signed-off-by: Maxime Coquelin <maxime.coquelin@redhat.com>
Reviewed-by: Jens Freimann <jfreimann@redhat.com>