Force Airflow DAGs repository update

Summary:
During development, we use force branch update workflow. That requires both
those options to allow Salt to fetch a non-forward branch, then to reset the
local branch.

This is a follow-up for de2fb22e.

Test Plan: salt dwellers state.apply roles/saas-airflow`

Reviewers: dereckson

Reviewed By: dereckson

Differential Revision: https://devcentral.nasqueron.org/D3286