Use same parameter for readconnroute router and readwritespiter to define maximum acceptable replication lag.

Maxscale readconnroute router uses parameter max_replication_lag while readwritespliter uses max_slave_replication_lag.

Customer requests a feature where readconnroute and readwritespliter both use the same parameter name.

Additionally the readconnrouter documentation refers to both max_slave_replication_lag and max_replication_lag. https://mariadb.com/kb/en/mariadb-maxscale-2302-readconnroute/#max_replication_lag