Revert "MINOR: ssl: rework add cert chain to CTX to be libssl independent"

Revert "MINOR: ssl: rework add cert chain to CTX to be libssl independent"

This reverts commit 4fed93eb725b513dd3b2029daa888311db110851.

This commit was simplifying the certificate chain loading with
SSL_CTX_add_extra_chain_cert() which is available in all SSL libraries.
Unfortunately this function is not compatible with the
multi-certificates bundles, which have the effect of concatenating the
chains of all certificate types instead of creating a chain for each
type (RSA, ECDSA etc.)

Should fix issue #655.