fix register cluster creates agent missing --cluster-namespace parameter

[yanfeng1992]

Signed-off-by: huangyanfeng huangyanfeng1992@gmail.com

What type of PR is this?
/kind bug

What this PR does / why we need it:

register cluster creates agent deployment missing --cluster-namespace parameter

Which issue(s) this PR fixes:
Fixes #

Special notes for your reviewer:

Does this PR introduce a user-facing change?:

`karmadactl`:  Fix register cluster creates agent missing --cluster-namespace parameter

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 53.31%. Comparing base (eb4a10d) to head (2a10b8b).

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Additional details and impacted files

@@            Coverage Diff             @@
##           master    #5005      +/-   ##
==========================================
+ Coverage   53.30%   53.31%   +0.01%     
==========================================
  Files         253      253              
  Lines       20560    20560              
==========================================
+ Hits        10959    10962       +3     
+ Misses       8875     8873       -2     
+ Partials      726      725       -1     

Flag	Coverage Δ
unittests	53.31% <ø> (+0.01%)	⬆️

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[RainbowMango]

Yeah, the option --cluster-namespace of karmadactl register is missed during register.

    --cluster-namespace='karmada-cluster':
	Namespace in the control plane where member cluster secrets are stored.

/lgtm
/approve

[karmada-bot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: RainbowMango

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