Idempotency for reverse proxy configuration settings

[tombosmansibm]

If you use the entries syntax in the reverse proxy entry configuration (web/configure_reverseproxy_instances) , idempotency does not always work.
In particular, it does not work for non-string entries.

Additionally, there's a number of rest requests to get the current configuration. It would be more efficient to get the configuration for a stanza once, and work with that.

[tombosmansibm]

#215 describes the same problem