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_mysql.cc

@@ -292,9 +292,8 @@ void check_session_command_reply(GWBUF *buffer, SRWBackend backend)
         err.append(replybuf + 8, 5);
         msg.append(replybuf + 13, replylen - 4 - 5);
 
-        MXS_ERROR("Failed to execute session command in [%s]:%d. Error was: %s %s",
-                  backend->server()->name, backend->server()->port,
-                  err.c_str(), msg.c_str());
+        MXS_ERROR("Failed to execute session command in %s. Error was: %s %s",
+                  backend->uri(), err.c_str(), msg.c_str());
     }
 }