Activating assign_data_in_buf callback.

Signed-off-by: Eyal Salomon <esalomon@mellanox.com>
Signed-off-by: Matt Benjamin <matt@linuxbox.com>
Disable Accelio internal mempools.

Vu Pham agrees that we should do this as well, even with a 0
size threshold for assign_data_in_buf callouts.

Signed-off-by: Matt Benjamin <matt@cohortfs.com>