Changes

smdpp_tests: extend comment with hint on CA cert locations

Let's extend the comment around mp_es2plus_server_host and mention that
CA certfiicates should be made availablein /etc/ssl/certs. In case the
CA certificate is not present in /etc/ssl/certs, libcurl will refuse
to connect.

Change-Id: I58d4f35c8493a9f9531da8d7c565760a08101e35
Related: SYS#7339