This move allows server to use it on #8868 as described in #8890

-- Relates: #8890

Extracted preamble code for making space to #8890 changes.

-- Related: #8890

This needs OpenSSL >= 1.1, otherwise it will keep using the scrypt
dependency.

We should think about deprecating scrypt as a dependency when we can be
sure that the adoption of libssl 1.1 is wide enough. I think that at
some point (soledad 0.11 or so) we can drop the scrypt dependency, which
was being somehow problematic at times (the _scrypt.so was not appearing
when installing with pip, needed workarounds). From that moment on, we
can raise an error if an old libssl is found and no scrypt can be
imported - leaving that to the user/packager.

In debian stretch and afterwards, you can get that version by installing
libssl-dev

- Related: #8472