apps/cmp.c: Free bio on error to avoid memory leak

apps/cmp.c: Free bio on error to avoid memory leak

Call BIO_free() to release bio if ASN1_i2d_bio_of() fails, preventing a memory leak.

Fixes: 6a3579e190 ("CMP: add support for requesting cert template using genm/genp")
Signed-off-by: JiashengJiang <jiasheng@purdue.edu>
Reviewed-by: Shane Lontis <shane.lontis@oracle.com>
Reviewed-by: Paul Dale <ppzgs1@gmail.com>
Reviewed-by: Tomas Mraz <tomas@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/27647)