Adds an `optional` value to the previously boolean `tls-auth-clients` configuration keyword.
Co-authored-by: Yossi Gottlieb <yossigo@gmail.com>
(cherry picked from commit f31260b0445f5649449da41555e1272a40ae4af7)
Seems like on some systems choosing specific TLS v1/v1.1 versions no
longer works as expected. Test is reduced for v1.2 now which is still
good enough to test the mechansim, and matters most anyway.
* Introduce a connection abstraction layer for all socket operations and
integrate it across the code base.
* Provide an optional TLS connections implementation based on OpenSSL.
* Pull a newer version of hiredis with TLS support.
* Tests, redis-cli updates for TLS support.
