Simplify CheckUnitUser logic

[a1012112796]

if check one user's unit in different repos, it's not necessary to get user data every time.

[codecov-commenter]

Codecov Report

Merging #12854 into master will decrease coverage by 0.02%.
The diff coverage is 64.28%.

@@            Coverage Diff             @@
##           master   #12854      +/-   ##
==========================================
- Coverage   43.11%   43.08%   -0.03%     
==========================================
  Files         655      655              
  Lines       72328    72329       +1     
==========================================
- Hits        31186    31165      -21     
- Misses      36094    36111      +17     
- Partials     5048     5053       +5     

Impacted Files	Coverage Δ
routers/home.go	47.50% <0.00%> (+0.36%)	⬆️
models/notification.go	65.83% <57.14%> (-1.22%)	⬇️
models/repo.go	55.54% <80.00%> (-0.15%)	⬇️
routers/repo/repo.go	28.46% <100.00%> (ø)
models/repo_mirror.go	2.38% <0.00%> (-11.91%)	⬇️
modules/cron/tasks_basic.go	87.35% <0.00%> (-3.45%)	⬇️
modules/notification/mail/mail.go	34.48% <0.00%> (-3.45%)	⬇️
modules/notification/ui/ui.go	80.55% <0.00%> (-2.78%)	⬇️
modules/process/manager.go	72.50% <0.00%> (-2.50%)	⬇️
services/pull/check.go	47.69% <0.00%> (-2.31%)	⬇️
... and 10 more

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[zeripath]

I suspect there are lots more improvements possible here.