Merge comparisons with "in" operator in DagBag

[kaxil]

This is faster, less verbose, and more readable.

---

Make sure to mark the boxes below before creating PR: [x]

• Description above provides context of the change
• Unit tests coverage for changes (not needed for documentation changes)
• Target Github ISSUE in description if exists
• Commits follow "How to write a good git commit message"
• Relevant documentation is updated including usage instructions.
• I will engage committers as explained in Contribution Workflow Example.

---

In case of fundamental code change, Airflow Improvement Proposal (AIP) is needed.
In case of a new dependency, check compliance with the ASF 3rd Party License Policy.
In case of backwards incompatible changes please leave a note in UPDATING.md.
Read the Pull Request Guidelines for more information.

[mik-laj]

Should it be detected by pylint or other linter?

[ashb]

Faster might not be true - the interpreter may well treat these the same. It won't be slower toug though

[kaxil]

Should it be detected by pylint or other linter?

Yup will take a look today on our pylint configs