fix: ServiceCidr + DNSServiceIP validation error message

[jackfrancis]

Reason for Change:

Fix misleading validation message for DNSServiceIP / ServiceCidr configuration combinations.

Issue Fixed:

Fixes #349

Requirements:

• uses conventional commit messages
• includes documentation
• adds unit tests
• tested upgrade from previous version

Notes:

[codecov]

Codecov Report

Merging #360 into master will not change coverage.
The diff coverage is 100%.

@@           Coverage Diff           @@
##           master     #360   +/-   ##
=======================================
  Coverage   53.22%   53.22%           
=======================================
  Files          95       95           
  Lines       14224    14224           
=======================================
  Hits         7571     7571           
  Misses       5988     5988           
  Partials      665      665

[CecileRobertMichon]

/lgtm

[acs-bot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: CecileRobertMichon, jackfrancis

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