Enable concat_newline setting in ssl::cert

Enable concat_newline on all use of concat in ssl::cert defined type

Without this commit, SSL certificates, key files, intermediate chains,
etc that get concatenated together can generate unusable combined files
if any of the input fragments lack a newline at the end of the file. In
that case, nginx/haproxy/apache will fail to start.

This commit uses the concat_newline parameter to ensure that all
fragments have trailing newlines, even if the input files lack them.