Detecting IP conflicts takes place before gateway detection, avoiding communication failure

[cyclinder]

Detect IP conflicts before gateway detection to fix gateway detection could potentially update the arp table causing communication fail

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Notice:

• unite test or E2E test
• do not forget essential code comment and log
• document for the PR
• release note label
  "release/none"
  "release/bug"
  "release/feature"
• read about Contribution notice: https://spidernet-io.github.io/spiderpool/latest/develop/contributing/

What issue(s) does this PR fix:

Fixes #4484

Special notes for your reviewer:

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 1.35%. Comparing base (ffcff3b) to head (dbd5ab0).
Report is 2 commits behind head on release-v1.0.

Additional details and impacted files

@@             Coverage Diff              @@
##           release-v1.0   #4507   +/-   ##
============================================
  Coverage          1.35%   1.35%           
============================================
  Files                56      56           
  Lines              6591    6591           
============================================
  Hits                 89      89           
  Misses             6492    6492           
  Partials             10      10           

Flag	Coverage Δ
unittests	1.35% <ø> (ø)

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