Dropping a schema that has a type used in a distribution column of a table fails

Reproducible on 10.2 (and maybe in older versions too):

```sql
create schema my_schema;
set search_path to my_schema;

create type my_type as (int_field int);
create table tbl (a my_schema.my_type);
SELECT create_distributed_table('tbl', 'a');

drop schema my_schema cascade;
-- ERROR: cache lookup failed for type 326845

set search_path to public;

drop schema my_schema cascade;
-- ERROR: cache lookup failed for type 326845

-- and here is how we can workaround "cache lookup failed" errors
drop table my_schema.tbl;
drop schema my_schema cascade;
```