Link bonding unit tests uses net_null vdev as slaves,
and trying to configure DEV_RX_OFFLOAD_CRC_STRIP as offload
flags to vdev is not correct as vdev doesn't support offloads.
The unit test is reporting this as failure, so fix this by
removing the offloads.
Fixes: c6698a3e8f ("ethdev: convert remaining apps to new offload API")
Signed-off-by: Reshma Pattan <reshma.pattan@intel.com>