CI: fix dch after adding the new 0.106.1 tag

[daniloegea]

After adding the new tag from the stable/0.106 branch, dch is failing with:

New version specified (0.106-78-g3074070) is less than
the current version number (0.106.1-0ubuntu1)! Use -b to force.

Basically, git describe is still describing the tag 0.106 and not 0.106.1.
With this change, we'll first find the lastest tag before calling describe.

Description

Checklist

• Runs make check successfully.
• Retains 100% code coverage (make check-coverage).
• New/changed keys in YAML format are documented.
• (Optional) Adds example YAML for new feature.
• (Optional) Closes an open bug in Launchpad.

[schopin-pro]

ACK. I haven't gone through all the scenarios in which this could fail down the line, and in the case of our CI config I figure a quickfix now is better than an hypothetical "correct" fix that doesn't yet exist.