reset uphold setting for agent service in flatcar distro

[nagworld9]

Description

New flatcar images set the uphold property for agent service that is causing automatic restart on stop cmd
[Upholds= dependency on it has a continuous effect, constantly restarting the unit if necessary]
Resetting the uphold property as workaround for now.

Issue #

---

PR information

• The title of the PR is clear and informative.
• There are a small number of commits, each of which has an informative message. This means that previously merged commits do not appear in the history of the PR. For information on cleaning up the commits in your pull request, see this page.
• If applicable, the PR references the bug/issue that it fixes in the description.
• New Unit tests were added for the changes made

Quality of Code and Contribution Guidelines

• I have read the contribution guidelines.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 71.64%. Comparing base (3aebcdd) to head (7526247).
Report is 232 commits behind head on develop.

❗ Current head 7526247 differs from pull request most recent head 8547e69. Consider uploading reports for the commit 8547e69 to get more accurate results

Additional details and impacted files

@@             Coverage Diff             @@
##           develop    #3066      +/-   ##
===========================================
- Coverage    71.97%   71.64%   -0.34%     
===========================================
  Files          103      110       +7     
  Lines        15692    16422     +730     
  Branches      2486     2351     -135     
===========================================
+ Hits         11295    11766     +471     
- Misses        3881     4105     +224     
- Partials       516      551      +35     

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

[narrieta]

let's turn it off rather than stopping it (otherwise it'll just restart on the next boot)

Configuration
There are three different strategies that locksmithd can use after the update engine has successfully applied an update:

etcd-lock - reboot after first taking a lock in etcd.
reboot - reboot without taking a lock.
off - causes locksmithd to exit and do nothing.
These strategies will either be followed immediately after an update, or during the next available [reboot window](https://github.com/flatcar/locksmith#reboot-windows) if one has been configured.

These strategies can be configured via /etc/flatcar/update.conf with a line that looks like:

REBOOT_STRATEGY=reboot

[nagworld9]

I tried this setting and its not effective until reboot. Maybe I need to check if service restart required.