fix some bug for raven l3 and ravne l7

[River-sh]

1. fix the bug of raven l7 is closed due to gateway is deleted
2. fix the bug of raven l3 can not config arp

[codecov]

Codecov Report

Attention: Patch coverage is 32.16783% with 97 lines in your changes are missing coverage. Please review.

Project coverage is 35.85%. Comparing base (fa158b9) to head (ab59000).
Report is 1 commits behind head on main.

Files	Patch %	Lines
pkg/networkengine/util/utils.go	0.00%	79 Missing ⚠️
pkg/networkengine/routedriver/vxlan/vxlan.go	71.87%	12 Missing and 6 partials ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #169      +/-   ##
==========================================
+ Coverage   35.63%   35.85%   +0.22%     
==========================================
  Files          12       12              
  Lines        1476     1570      +94     
==========================================
+ Hits          526      563      +37     
- Misses        842      893      +51     
- Partials      108      114       +6     

Flag	Coverage Δ
unittests	35.85% <32.16%> (+0.22%)	⬆️

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