crypto: testmgr - remove extra bytes from 3DES-CTR IVs

3DES only has an 8-byte block size, but the 3DES-CTR test vectors use
16-byte IVs.  Remove the unused 8 bytes from the ends of the IVs.

Signed-off-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>