Do not ignore schema of a table

[Denchick]

When you are adding a new table, you can specify a schema. For example:

ALTER DISTRIBUTION ds1 ATTACH RELATION schema_name.table_name DISTRIBUTION KEY id;

In fact, during query/transaction routing, the schema is not taken into account. If there are tables with the same name but different schemas, they will be incorrectly routed. To fix this bug, you have to remember about search_path as well.