Add name and uri helpers to Backend

Providing helper functions for the commonly used parts of the server makes
code easier to read. It also removes any possibility for formatting
problems by moving the URI and name string handling inside the Backend
class.

server/modules/routing/readwritesplit/rwsplit_session_cmd.cc

@@ -61,7 +61,7 @@ void process_sescmd_response(ROUTER_CLIENT_SES* rses, SRWBackend& backend,
                 {
                     MXS_ERROR("Slave server '%s': response differs from master's response. "
                               "Closing connection due to inconsistent session state.",
-                              backend->server()->unique_name);
+                              backend->name());
                     backend->close(mxs::Backend::CLOSE_FATAL);
                     *pReconnect = true;
                 }