Bug 3017 - Error messages and logs missing for this or other RPC failures

Bug 3017 - Error messages and logs missing for this or other RPC failures

Note: Restconf doesn't contain logs for more functionality (not only RPC)
so this patch adds better logging for Restconf (BrokerFacade and RestconfImpl).
Administrators are not able to pair user's reports and karaf log without better
logging information and it would help for better problem identify (e.g. bug 3080).

* BrokerFacade - add Logging for lev info for all extra state
* RestconfImpl - add Logging for lev warn for unexpected error state
               - add Logging for lev debug for another extra state

Change-Id: I452dddd4fb9d75a7754be0bc1d92518dcb1eb786
Signed-off-by: Vaclav Demcak <vdemcak@cisco.com>