UI: Fix issue update race condition

[silverwind]

#5980 introduced a race condition where location.reload would in some browers fire before the async ajax request in updateIssuesMeta to update a issue label was completed. Fixed this by letting updateIssuesMeta return a Promise and only executing the reload after all requests have finished.

Also introduced a shared reload function.

Fixes: #6191

[codecov-io]

Codecov Report

Merging #6194 into master will increase coverage by <.01%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master    #6194      +/-   ##
==========================================
+ Coverage   38.86%   38.86%   +<.01%     
==========================================
  Files         354      354              
  Lines       50210    50210              
==========================================
+ Hits        19512    19516       +4     
+ Misses      27872    27867       -5     
- Partials     2826     2827       +1

Impacted Files	Coverage Δ
models/repo_list.go	66.84% <0%> (-1.06%)	⬇️
routers/repo/view.go	42.07% <0%> (+0.99%)	⬆️
models/unit.go	14.28% <0%> (+14.28%)	⬆️

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[zeripath]

Hmm... Do we have a Promise library already installed for IE?

[silverwind]

Hmm... Do we have a Promise library already installed for IE?

Yes, we do have a Promise polyfill, but it was so far only loaded when heatmap was enabled. Just fixed that so it is always loaded.

[silverwind]

Replaced es6-promise with promise-polyfill. Not sure if the former does automatically polyfill window.Promise, but the latter one surely does. Testing IE now.

[silverwind]

IE11 fixed and working, it actually choked on ES6 trailing commas, took me a while to realize.

[jolheiser]

Tested with Chrome, Firefox, and IE11 using @sapk checkout PR contrib, worked on all browsers.