Removed libzstd from "buildrequires" As it turns out we require to build the libzstd package from source ourself which is only be done if the package is NOT installed. Using --source-deps-only failed due open issues in the current librdkafka branch, so this is the best solution so far.
updated etc-mock files to allow networking during build. This is required if we build libraries from source during make.
With the changes above, static librdkafka libraries are build again which will solve the "undefined symbol" issues in rsyslog packages. See also: https://github.com/rsyslog/rsyslog/issues/4966
closes: https://github.com/rsyslog/rsyslog-pkg-rhel-centos/issues/116