lookml ingestion broken for cascading derived tables

[remisalmon]

Describe the bug
Cascading derived tables are no longer ingested properly in DataHub.

When cascading derived tables are used in lookml views (see https://docs.looker.com/data-modeling/learning-lookml/derived-tables#cascading_derived_tables), they now get ingested as datasets from the upstream platform/connection instead of views from the same platform (looker).

This bug was introduced here in lookml.py: https://github.com/linkedin/datahub/pull/3255/files#diff-49de7c0eb38108e88215470de34a7d77a8d4ca25878877a2670e55864532341eL546-R683

To Reproduce
Steps to reproduce the behavior:

1. Define a lookml view using cascading derived tables (i.e. refer a table defined in another view)
2. Ingest lookml
3. The lineage tab of the UI shows the wrong upstream platform

Expected behavior
The proper upstream platform (in this case the same platform, looker) should be shown.

Additional context
DataHub version: 0.8.13
acryl-datahub version: 0.8.13.1

[shirshanka]

@remisalmon: could you verify if #3262 fixes the issue for you?

[remisalmon]

It does, thank you!