feat: optimize trigger download task return empty

[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

Merging #2958 (9df25c5) into main (ec66fd1) will increase coverage by 0.00%.
The diff coverage is 76.92%.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #2958   +/-   ##
=======================================
  Coverage   51.03%   51.03%           
=======================================
  Files         161      161           
  Lines       21904    21899    -5     
=======================================
- Hits        11179    11177    -2     
+ Misses      10063    10060    -3     
  Partials      662      662           

Flag	Coverage Δ
Object-compatibility-e2etests	?
e2etests	?
unittests	51.03% <76.92%> (+<0.01%)	⬆️

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

Files	Coverage Δ
scheduler/resource/seed_peer.go	23.35% <100.00%> (ø)
scheduler/resource/seed_peer_client_mock.go	24.32% <100.00%> (-0.68%)	⬇️
scheduler/service/service_v2.go	84.93% <100.00%> (-0.05%)	⬇️
scheduler/resource/seed_peer_mock.go	0.00% <0.00%> (ø)

... and 2 files with indirect coverage changes