[PATCH 0 of 6] SSL tests refactoring fixes

[Sergey Kandaurov]

This series fixes various issues arised post SSL tests simplification,
seen on various distributions with old OpenSSL and/or Perl, most notably:
- Amazon Linux (LTS)
ssl_certificate.t
ssl_certificates.t
stream_ssl_certificate.t
stream_ssl_variables.t
- CentOS 7
ssl_certificate.t
stream_ssl_certificate.t
stream_ssl_variables.t
- SLES 12
mail_ssl.t
ssl_certificates.t
ssl_stapling.t
stream_ssl_variables.t
mail_ssl_session_reuse.t
stream_ssl_session_reuse.t
- LibreSSL
ssl_stapling.t