Detect cycle automatically in update_config script

Description

It's rather annoying to require both cycle and proposal as input for update_config manually. This MR adds auto detection of cycle of omitted by looking up the proposal's path on GPFS.

How Has This Been Tested?

Unit tests.

Types of changes

• New feature (non-breaking change which adds functionality)

Checklist:

• My code follows the code style of this project.
• I added tests where appropriate.

Reviewers

@kluyvert