app/testpmd: fix bonding initialization

when creating a bond device in testpmd, a name for a device must meet
the correct convention described in the documentation:
The device name must start with the net_bonding prefix
followed by numbers or letters.
Change for ALB mempool allocation - mem_name was too long.

Fixes: 9bf4901d1a11 ("bus/vdev: remove probe with driver name option")
Cc: stable@dpdk.org
Signed-off-by: Michal Jastrzebski <michalx.k.jastrzebski@intel.com>
Reviewed-by: Jingjing Wu <jingjing.wu@intel.com>