Add support for NodePort-type service

[Kuromesi]

Ⅰ. Describe what this PR does

Set the nodePort of the canary service to 0 in order to support a NodePort-type service. This will result in a random nodePort being allocated to the canary service, thereby avoiding any port conflicts.

Ⅱ. Does this pull request fix one issue?

Ⅲ. Special notes for reviews

[codecov-commenter]

Codecov Report

Merging #170 (116337e) into master (72e1c0b) will increase coverage by 0.43%.
Report is 2 commits behind head on master.
The diff coverage is 100.00%.

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@@            Coverage Diff             @@
##           master     #170      +/-   ##
==========================================
+ Coverage   43.44%   43.87%   +0.43%     
==========================================
  Files          50       50              
  Lines        5361     5374      +13     
==========================================
+ Hits         2329     2358      +29     
+ Misses       2635     2618      -17     
- Partials      397      398       +1     

Flag	Coverage Δ
unittests	43.87% <100.00%> (+0.43%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Files Changed	Coverage Δ
pkg/trafficrouting/manager.go	52.40% <100.00%> (+15.30%)	⬆️

... and 1 file with indirect coverage changes

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[zmberg]

/lgtm

[zmberg]

/approve

[kruise-bot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: zmberg

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