Sanity checking in gost_grasshopper_cipher_cleanup

Fixed GOST_PK_FORMAT param

Reported-by: Gleb Fotengauer-Malinovskiy <glebfm@altlinux.org>

Openssl is already have output result size in EVP_MD.md_size
We should not exceed its value when writing digest output.
This should be fixed more consistently, probably, by removing
dgst_size from OMAC_CTX.

Openssl copies a state between valid contexts. But, EVP_MD_CTX_copy_ex
just memcpy-s private data (md_data), which points to OMAC_CTX), which
have pointer to CMAC_CTX. Copying pointer makes CMAC context just the
same on the both sides. As a consequence, we can not do normal copy of a
state between CMAC contexts. As a fix, we just clone it if it's equal
between copy sides.

Reported-by: Gleb Fotengauer-Malinovskiy <glebfm@altlinux.org>