fix: use testify instead of t.Fatal or t.Error in server package (part 1)

[mmorel-35]

Description

This uses testify instead of testing for t.Fatal or t.Error calls in server package

Related to #18972

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is NOT APPROVED

This pull-request has been approved by: mmorel-35
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[k8s-ci-robot]

Hi @mmorel-35. Thanks for your PR.

I'm waiting for a etcd-io member to verify that this patch is reasonable to test. If it is, they should reply with /ok-to-test on its own line. Until that is done, I will not automatically test new commits in this PR, but the usual testing commands by org members will still work. Regular contributors should join the org to skip this step.

Once the patch is verified, the new status will be reflected by the ok-to-test label.

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[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 68.73%. Comparing base (c1171da) to head (4ab4c38).

Additional details and impacted files

see 27 files with indirect coverage changes

@@            Coverage Diff             @@
##             main   #18971      +/-   ##
==========================================
- Coverage   68.77%   68.73%   -0.05%     
==========================================
  Files         420      420              
  Lines       35623    35623              
==========================================
- Hits        24500    24484      -16     
- Misses       9694     9716      +22     
+ Partials     1429     1423       -6     

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[ahrtr]

/ok-to-test

[mmorel-35]

/test pull-etcd-verify