crypto: testmgr - move to generic async completion

testmgr is starting async. crypto ops and waiting for them to complete.
Move it over to generic code doing the same.

This also provides a test of the generic crypto async. wait code.
Signed-off-by: Gilad Ben-Yossef <gilad@benyossef.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>