examples/fips_validation: fix CMAC test

examples/fips_validation: fix CMAC test

As a result of the cmac test running the test where
PT len is 65536 it should give a result back to the
user USER1: Error -1: Prepare op USER1: PT len 65536
as this MSG len is not supported. Issue was
that the application was not freeing the op properly after
a while causing the app to fail.

CRYPTODEV: rte_cryptodev_sym_session_create() line 1340:
couldn't get object from session mempool
USER1: Error -12: test block
USER1: Error -12: Failed test CMAC/req/CMAC.req

Fixes: cd255ccf5764 ("examples/fips_validation: support AES parsing")
Cc: stable@dpdk.org
Signed-off-by: Marko Kovacevic <marko.kovacevic@intel.com>