MXS-1503: Remove false debug assertion

It is possible that the routing fails even if master_reconnection is
enabled and a second master is available. This is the case when a
transaction is open or autocommit is disabled which is what the
mxs359_master_switch test tests.

server/modules/routing/readwritesplit/rwsplit_route_stmt.cc

@@ -746,7 +746,6 @@ void RWSplitSession::log_master_routing_failure(bool found,
     else if (old_master && curr_master && old_master->in_use())
     {
         /** We found a master but it's not the same connection */
-        ss_dassert(!m_config.master_reconnection);
         ss_dassert(old_master != curr_master);
         sprintf(errmsg, "Master server changed from '%s' to '%s'",
                 old_master->name(), curr_master->name());