[ISSUE #525][operator] refine svc creations

[advancedxy]

What changes were proposed in this pull request?

1. generate headless svc for coordinators and pass this service to shuffle servers
2. makes RPCNodePort/HTTPNodePort optional for coordinators
3. remove service creation for shuffle servers.

Why are the changes needed?

This fixes #525

Does this PR introduce any user-facing change?

No

How was this patch tested?

It has already been manually verified, and will add more UTs.

[advancedxy]

ping @wangao1236 to see if you have any other input.

[advancedxy]

ping @wangao1236 this should be ready for review.

[advancedxy]

Gently ping @wangao1236.

[codecov-commenter]

Codecov Report

Merging #530 (8c7ad99) into master (cf9afab) will increase coverage by 1.15%.
The diff coverage is 96.15%.

@@             Coverage Diff              @@
##             master     #530      +/-   ##
============================================
+ Coverage     59.69%   60.85%   +1.15%     
  Complexity     1795     1795              
============================================
  Files           213      213              
  Lines         12414    12372      -42     
  Branches       1050     1050              
============================================
+ Hits           7411     7529     +118     
+ Misses         4594     4435     -159     
+ Partials        409      408       -1     

Impacted Files	Coverage Δ
...pkg/controller/sync/shuffleserver/shuffleserver.go	85.78% <0.00%> (+24.55%)	⬆️
...bernetes/operator/pkg/controller/controller/rss.go	35.36% <100.00%> (+0.22%)	⬆️
...tor/pkg/controller/sync/coordinator/coordinator.go	97.87% <100.00%> (+31.89%)	⬆️
...y/kubernetes/operator/pkg/webhook/inspector/rss.go	59.25% <100.00%> (+0.61%)	⬆️

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