Fix collectResultLoop hang after search timeout

[xige-16]

fix issue: #15209
/kind bug
Signed-off-by: xige-16 [email protected]

[longjiquan]

thx for finding out this bug. Maybe we should always use channel with cache?
/lgtm

[czs007]

/approve

[sre-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

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[codecov]

Codecov Report

Merging #15250 (9d67cab) into master (871e093) will decrease coverage by 0.02%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master   #15250      +/-   ##
==========================================
- Coverage   79.71%   79.69%   -0.03%     
==========================================
  Files         449      449              
  Lines       61244    61244              
==========================================
- Hits        48820    48807      -13     
- Misses      10091    10108      +17     
+ Partials     2333     2329       -4     

Impacted Files	Coverage Δ
internal/proxy/impl.go	83.71% <100.00%> (-0.78%)	⬇️
...nternal/util/rocksmq/client/rocksmq/client_impl.go	75.63% <0.00%> (-1.69%)	⬇️
internal/indexnode/indexnode_mock.go	83.71% <0.00%> (-1.14%)	⬇️
internal/indexcoord/index_coord.go	79.08% <0.00%> (-0.30%)	⬇️
internal/querycoord/task.go	81.04% <0.00%> (-0.20%)	⬇️
internal/rootcoord/root_coord.go	79.26% <0.00%> (-0.13%)	⬇️
internal/indexcoord/meta_table.go	83.28% <0.00%> (+0.26%)	⬆️
internal/rootcoord/task.go	77.42% <0.00%> (+0.43%)	⬆️
internal/querycoord/task_scheduler.go	76.92% <0.00%> (+0.59%)	⬆️
... and 3 more