Log Messages: Incorrect error message with remove node + citus local table

When we have a cluster with worker nodes, say 1 + 3, if we try to remove the coordinator when a citus local table exists, we get the following error:

```
SELECT master_remove_node('localhost', :master_port);
ERROR: cannot remove the last worker node because there are reference tables and it would cause data loss on reference tables
```

The error says that this is the last worker node, but it is not. The error should clarify that there exists `citus_local` tables in the coordinator, or it could say something to explicitly show `there is data in this node, which is only on this node`.

I think a nice improvement could be to show the table names in the error detail so that users know which tables should be considered.