Regression tests fail when citus is present and contrib_regression database is not created

Observed this issue when running regression tests on local machine
- citus extension is loaded (shared_preload_libraries)
- citus extension is created
- cstore_fdw is loaded
- cstore_fdw extension is created

Running make installcheck failed with
```
============== dropping database "contrib_regression" ==============
ERROR: database "contrib_regression" does not exist
command failed: "/usr/local/pgsql/bin/psql" -X -c "DROP DATABASE IF EXISTS \"contrib_regression\"" "postgres"
```

It succeeded as soon as I drop citus extension.