Fixed the mac of host veth side && cleanup dirty neigh table

[cyclinder]

What this PR does / why we need it:

Fixed the mac of host veth side && cleanup dirty neigh table

Which issue(s) this PR fixes:

Fixes #

Special notes for your reviewer:

[codecov]

Codecov Report

Merging #189 (428d864) into main (7ce3d60) will decrease coverage by 1.07%.
The diff coverage is 16.66%.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #189      +/-   ##
==========================================
- Coverage   64.75%   63.69%   -1.07%     
==========================================
  Files           5        5              
  Lines        1413     1446      +33     
==========================================
+ Hits          915      921       +6     
- Misses        428      451      +23     
- Partials       70       74       +4     

Flag	Coverage Δ
unittests	63.69% <16.66%> (-1.07%)	⬇️

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Files	Coverage Δ
pkg/utils/utils.go	73.25% <0.00%> (ø)
plugins/veth/veth.go	51.46% <17.02%> (-2.92%)	⬇️