apparmor: Fix kunit test for out of bounds array

The apparmor kunit tests are failing on the out of bounds array check
with the following failure

  # policy_unpack_test_unpack_array_out_of_bounds: EXPECTATION FAILED at security/apparmor/policy_unpack_test.c:178
  Expected unpack_array(puf->e, name, &array_size) == 1, but
  unpack_array(puf->e, name, &array_size) == -1
  # policy_unpack_test_unpack_array_out_of_bounds: EXPECTATION FAILED at security/apparmor/policy_unpack_test.c:180
  Expected array_size == 0, but
  array_size == 64192
  not ok 5 - policy_unpack_test_unpack_array_out_of_bounds

This is because unpack_array changed to allow distinguishing between
the array not being present and an error. In the error case the array
size is not set and should not be tested.

Reported-by: kernel test robot <yujie.liu@intel.com>
Fixes: 995a5b64620e ("apparmor: make unpack_array return a trianary value")
Signed-off-by: John Johansen <john.johansen@canonical.com>