Reencode certificates in X509_sign_ctx.
Reencode certificates in X509_sign_ctx.

Reencode certificates in X509_sign_ctx as well as X509_sign.

This was causing a problem in the x509 application when it modified an
existing certificate.

openssl/openssl,openssl/openssl,openssl/openssl,openssl/openssl,openssl/openssl,openssl/openssl