CREATE FOREIGN TABLE IF NOT EXISTS throws an error if the stream already exists

[hedayat]

This command is expected to not throw an error when the foreign table exists, but currently it prints an error related to pipelinedb:

CREATE FOREIGN TABLE IF NOT EXISTS alerts (...) SERVER pipelinedb;

NOTICE: relation "alerts" already exists, skipping
ERROR: duplicate key value violates unique constraint "pipeline_stream_relid_index"