citus_lock_waits shows that `CREATE INDEX CONCURRENTLY` blocks itsellf

Even if you run a single command like:
```SQL
create index concurrently i10 on users_table(user_id);
```

The citus_lock_waits shows that the process blocks itself:

```SQL
select * from citus_lock_waits;
┌─[ RECORD 1 ]──────────────────────────┬────────────────────────────────────────────────────────┐
│ waiting_gpid │ 40000013780 │
│ blocking_gpid │ 40000013780 │
│ blocked_statement │ create index concurrently i10 on users_table(user_id); │
│ current_statement_in_blocking_process │ create index concurrently i10 on users_table(user_id); │
│ waiting_nodeid │ 4 │
│ blocking_nodeid │ 4 │
└───────────────────────────────────────┴────────────────────────────────────────────────────────┘

```