Fixes #12124: Add post-hook to the manage key-value file techniques

[peckpeck]

https://www.rudder-project.org/redmine/issues/12124

[Normation-Quality-Assistant]

This PR breaks qa-test

-- stdout -- 
Your branch is up-to-date with 'NRM/branches/rudder/4.1'.
Already up-to-date.
Deleted branch 4.1_test (was 8b44d74).
Merge made by the 'recursive' strategy.
[...]
Running merge tests
 $ cd "/var/lib/quality-assistant/rudder-techniques" && ./qa-test --merge

-- stderr --
From github.com:peckpeck/rudder-techniques
 * [new branch]      ust_12124/add_post_hook_to_the_manage_key_value_file_techniques -> ust_12124/add_post_hook_to_the_manage_key_value_file_techniques_pr
Switched to branch 'branches/rudder/4.1'
Switched to a new branch '4.1_test'
make: *** [test] Error 1

You should run ./qa-test in your repository to make sure it works.
You can also run rudder-dev merge https://github.com/Normation/rudder-techniques/pull/1255 --test to test with upmerging.
After this, you can remove the Ready for merge tag
-- Your faithful QA

[peckpeck]

Commit modified

[Normation-Quality-Assistant]

This PR is not mergeable to upper versions.
Since it is "Ready for merge" you must merge it by yourself using the following command:
rudder-dev merge https://github.com/Normation/rudder-techniques/pull/1255
-- Your faithful QA

[peckpeck]

OK, merging this PR