feat: use real kubernetes server address to yurthub when yurtadm join

[Lan-ce-lot]

What type of PR is this?

Uncomment only one /kind <> line, hit enter to put that in a new line, and remove leading whitespace from that line:
/kind bug
/kind documentation
/kind enhancement
/kind good-first-issue
/kind feature
/kind question
/kind design
/sig ai
/sig iot
/sig network
/sig storage

What this PR does / why we need it:

In the scenario where the user forgets to set the yurthub server address for the master node, the yurtadm join command should replace the yurthub parameter with the address obtained from the join.

Which issue(s) this PR fixes:

Fixes #
#1474

Special notes for your reviewer:

Does this PR introduce a user-facing change?

other Note

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In response to this:

What type of PR is this?

Uncomment only one /kind <> line, hit enter to put that in a new line, and remove leading whitespace from that line:
/kind bug
/kind documentation
/kind enhancement
/kind good-first-issue
/kind feature
/kind question
/kind design
/sig ai
/sig iot
/sig network
/sig storage

What this PR does / why we need it:

In the scenario where the user forgets to set the yurthub server address for the master node, the yurtadm join command should replace the yurthub parameter with the address obtained from the join.

Which issue(s) this PR fixes:

Fixes #
#1474

Special notes for your reviewer:

Does this PR introduce a user-facing change?

other Note

Instructions for interacting with me using PR comments are available here. If you have questions or suggestions related to my behavior, please file an issue against the kubernetes/test-infra repository.

[codecov]

Codecov Report

Merging #1517 (8f92b63) into master (b99c905) will decrease coverage by 0.36%.
The diff coverage is 60.00%.

@@            Coverage Diff             @@
##           master    #1517      +/-   ##
==========================================
- Coverage   50.74%   50.38%   -0.36%     
==========================================
  Files         131      132       +1     
  Lines       15576    15707     +131     
==========================================
+ Hits         7904     7914      +10     
- Misses       6951     7070     +119     
- Partials      721      723       +2     

Flag	Coverage Δ
unittests	50.38% <60.00%> (-0.36%)	⬇️

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

Impacted Files	Coverage Δ
pkg/yurtadm/util/yurthub/yurthub.go	9.16% <60.00%> (ø)

... and 1 file with indirect coverage changes

[sonarcloud]

Kudos, SonarCloud Quality Gate passed!   

0 Bugs
0 Vulnerabilities
0 Security Hotspots
0 Code Smells

No Coverage information
0.1% Duplication

[openyurt-bot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: Lan-ce-lot, rambohe-ch

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[rambohe-ch]

/lgtm