fix mac address for vxlan

[codecov[bot]]

Codecov Report

Attention: Patch coverage is 48.71795% with 20 lines in your changes are missing coverage. Please review.

Project coverage is 35.75%. Comparing base (8a2c1ac) to head (d70eb16). Report is 3 commits behind head on main.

Files	Patch %	Lines
pkg/networkengine/routedriver/vxlan/vxlan.go	48.71%	14 Missing and 6 partials :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #168 +/- ## ========================================== - Coverage 35.82% 35.75% -0.07% ========================================== Files 12 12 Lines 1446 1474 +28 ========================================== + Hits 518 527 +9 - Misses 827 840 +13 - Partials 101 107 +6 ``` | [Flag](https://app.codecov.io/gh/openyurtio/raven/pull/168/flags?src=pr&el=flags&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=openyurtio) | Coverage Δ | | |---|---|---| | [unittests](https://app.codecov.io/gh/openyurtio/raven/pull/168/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=openyurtio) | `35.75% <48.71%> (-0.07%)` | :arrow_down: | Flags with carried forward coverage won't be shown. [Click here](https://docs.codecov.io/docs/carryforward-flags?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=openyurtio#carryforward-flags-in-the-pull-request-comment) to find out more.

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