Define commands as a dictionary instead of a tuple

Summary:
The extraneous comma made commands parsed as a tuple,
not as intended as a dictionary.

This caused any issue to fail the following test:
<command> in commands, as the tuple doesn't have named keys.

Ref T1647.

Test Plan: bats scripts/bats/test_edit_acme_dns_accounts.sh

Reviewers: dereckson

Reviewed By: dereckson

Maniphest Tasks: T1647

Differential Revision: https://devcentral.nasqueron.org/D2406