test/distributor: fix mbuf leak on failure

test/distributor: fix mbuf leak on failure

rte_mempool_get_bulk is used to get bufs/many_bufs from the pool,
but at some locations when test fails the bufs/many_bufs are
not returned back to the pool.
Due to this, multiple executions of distributor_autotest gives the
following error message: Error getting mbufs from pool.
To resolve this issue rte_mempool_put_bulk is used whenever the test
fails and returns.

Fixes: c3eabff124e6 ("distributor: add unit tests")
Cc: stable@dpdk.org
Signed-off-by: Sarosh Arif <sarosh.arif@emumba.com>
Acked-by: Lukasz Wojciechowski <l.wojciechow@partner.samsung.com>
Reviewed-by: David Hunt <david.hunt@intel.com>