crypto: api - Fix liveliness check in crypto_alg_tested

crypto: api - Fix liveliness check in crypto_alg_tested

As algorithm testing is carried out without holding the main crypto
lock, it is always possible for the algorithm to go away during the
test.

So before crypto_alg_tested updates the status of the tested alg,
it checks whether it's still on the list of all algorithms.  This
is inaccurate because it may be off the main list but still on the
list of algorithms to be removed.

Updating the algorithm status is safe per se as the larval still
holds a reference to it.  However, killing spawns of other algorithms
that are of lower priority is clearly a deficiency as it adds
unnecessary churn.

Fix the test by checking whether the algorithm is dead.

Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>