[Release 1.29] Add a guardrail for etcd-snapshot

[manuelbuil]

Backport: #11314
Issue: #11391

FOR JANUARY RELEASE

[codecov]

Codecov Report

Attention: Patch coverage is 72.72727% with 3 lines in your changes missing coverage. Please review.

Project coverage is 42.33%. Comparing base (7a4d8fc) to head (2db50f9).

Files with missing lines	Patch %	Lines
pkg/cluster/managed.go	72.72%	2 Missing and 1 partial ⚠️

Additional details and impacted files

@@               Coverage Diff                @@
##           release-1.29   #11395      +/-   ##
================================================
- Coverage         46.77%   42.33%   -4.45%     
================================================
  Files               179      179              
  Lines             18720    18730      +10     
================================================
- Hits               8756     7929     -827     
- Misses             8613     9602     +989     
+ Partials           1351     1199     -152     

Flag	Coverage Δ
e2etests	34.46% <72.72%> (-7.74%)	⬇️
inttests	34.77% <72.72%> (-0.01%)	⬇️
unittests	13.73% <0.00%> (-0.01%)	⬇️

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