Prepare for clustered RabbitMQ (DE237) and add a delim to rcb_safe_deref

rcb_safe_deref needs an additional option for the delimiter character
so we can deref on things that include a "." today.  You still need
strong knowledge of what's in the string that you are derefing.

The default remains unchanged with the delim="."

This also removes the sysctl junk globally as we won't need it soon.