pfSense

Improvements to plugin_xmlrpc functions

- The "merged in config" log may not show all merged sections. Fix this by
not clobbering the "$sections" variable.
- Fix variable expansion in the xmlrpc_recv plugin error logs.
- Pass the return value of "plugin_xmlrpc_recv" to
"plugin_xmlrpc_recv_done" and introduce the magic string
"xmlrpc_recv_result" within the return value. This allows packages to
define the result and act on it after the sync is done. For example the
package may only want to restart in "plugin_xmlrpc_recv_done" when there
have been config changes with the call to "plugin_xmlrpc_recv".