test: refactor e2e testings of the client leaving

[gaius-qi]

Description

Related Issue

Motivation and Context

Screenshots (if appropriate)

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
• Documentation Update (if none of the other choices apply)

Checklist

• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have read the CONTRIBUTING document.
• I have added tests to cover my changes.

[codecov]

Codecov Report

Attention: Patch coverage is 0% with 15 lines in your changes missing coverage. Please review.

Project coverage is 35.80%. Comparing base (071072f) to head (5df34b0).
Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
scheduler/service/service_v2.go	0.00%	13 Missing ⚠️
manager/job/sync_peers.go	0.00%	1 Missing ⚠️
scheduler/resource/standard/host.go	0.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3590      +/-   ##
==========================================
- Coverage   36.03%   35.80%   -0.24%     
==========================================
  Files         335      335              
  Lines       36961    36962       +1     
==========================================
- Hits        13320    13234      -86     
- Misses      22804    22889      +85     
- Partials      837      839       +2     

Flag	Coverage Δ
unittests	35.80% <0.00%> (-0.24%)	⬇️

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

Files with missing lines	Coverage Δ
pkg/idgen/host_id.go	100.00% <ø> (ø)
manager/job/sync_peers.go	0.00% <0.00%> (ø)
scheduler/resource/standard/host.go	88.23% <0.00%> (ø)
scheduler/service/service_v2.go	72.16% <0.00%> (-8.08%)	⬇️

... and 3 files with indirect coverage changes

[BruceAko]

LGTM

[chlins]

lgtm