fix(ug_util): prioritize user-data.users over the default user config

[mostafaCamel]

Proposed Commit Message

fix(ug_util): prioritize user-data.users over the default user config

Fixes GH-6703

Additional Context

Test Steps

.tox/py3/bin/python -m pytest -vv tests/unittests/distros/test_user_data_normalize.py::TestUGNormalize

Merge type

• Squash merge using "Proposed Commit Message"
• Rebase and merge unique commits. Requires commit messages per-commit each referencing the pull request number (#<PR_NUM>)

[mostafaCamel]

The first commit I pushed is failing as expected as I only added the unit test

The expected failure

TOTAL                                                          33026   6291  12224   1597    79%
=========================== short test summary info ============================
FAILED tests/unittests/distros/test_user_data_normalize.py::TestUGNormalize::test_users_dict_override_default_attribute - assert True is False
= 1 failed, 5641 passed, 5 skipped, 13 xfailed, 2 xpassed, 84 warnings in 118.45s (0:01:58) =
py3: exit 1 (129.32 seconds) /home/runner/work/cloud-init/cloud-init> .tox/py3/bin/python -m pytest -vv --cov=cloudinit --cov-branch --color=yes pid=2384
  py3: FAIL code 1 (135.99=setup[6.67]+cmd[129.32] seconds)
  evaluation failed :( (136.04 seconds)
Error: Process completed with exit code 1.

[mostafaCamel]

#6703

[mostafaCamel]

After pushing the code fix, all the unit tests now pass

[holmanb]

Please add an integration test.

[mostafaCamel]

Note to myself about the integration tests (will work on it the weekend):

• Declare 2 contansts the python integration: a plain-text password and its hash
  • I first need to run openssl passwd -6 "yourplainpassword" on your terminal to generate the hash and pass it as a constant in the python script
• 2 ubuntu lxc containers A (with cloud-config.users ["default", {"name": "ubuntu", "hashed_passwd": "superpassword"}]) and B (with cloud-config.users ["default", {"name": "ubuntu", "hashed_passwd": "superpassword", "lock_passwd": False}])
• confirm that the 2 contianers are up and running ( I don't know if the test helpers have such a function... can skip it given the following steps)
• grep -E "^ubuntu:!<hashedpassword>: /etc/shadow for container A (and that there is only one occurence) ... notice the exclamation amrk as it indicates the password is locked
• grep -E "^ubuntu:!<hashedpassword>: /etc/shadow for container B (and that there is only one occurence)
  • No need to confirm there is there is only one occurrence in grep as ^ubuntu: is enough as usernames are unique
• Console access to container A should fail
• Console access to container B should succeed