remove redundant call to 'notify_tac_cancelled'.

[marcofavorito]

Proposed changes

Describe the big picture of your changes here to communicate to the maintainers why we should accept this pull request.

When there are not enough agents to start a TAC, there is a redundant call to notify_tac_cancelled(), which caused the controller agent to send the Cancelled message twice.

Fixes

None.

Types of changes

What types of changes does your code introduce to agents-tac? Put an x in the boxes that apply

• [X] Bugfix (non-breaking change which fixes an issue)
• [ ] New feature (non-breaking change which adds functionality)
• [ ] Breaking change (fix or feature that would cause existing functionality to not work as expected)

Checklist

Put an x in the boxes that apply.

• [X] I have read the CONTRIBUTING doc
• [X] I am making a pull request against the develop branch (left side). Also you should start your branch off our develop.
• [X] Lint and unit tests pass locally with my changes
• [ ] I have added tests that prove my fix is effective or that my feature works
• [ ] I have added necessary documentation (if appropriate)
• [ ] Any dependent changes have been merged and published in downstream modules

Further comments

None.