tests: Fix dpdk-link unit test

- Add missing free and alloc mock queues to test case.
- Remove unit test that checked for failures during mbuf allocation. Not
  valid anymore with new alloc queue model.

Change-Id: Icf51d8f72821665ed57369558a4f742437aa82e9
Signed-off-by: Nicolas Pernas Maradei <nicolasx.pernas.maradei@intel.com>