Use constant backoff for DownloadOSURL

[red-0ne]

Implement a constant backoff with 1 second interval and 15 retries for osclient.DownloadOSURL

Closes #209

[codecov]

Codecov Report

Merging #210 (404f085) into main (5dde9a5) will increase coverage by 0.05023%.
The diff coverage is 100.00000%.

@@                 Coverage Diff                 @@
##                main        #210         +/-   ##
===================================================
+ Coverage   51.15800%   51.20823%   +0.05023%     
===================================================
  Files             29          29                 
  Lines           1943        1945          +2     
===================================================
+ Hits             994         996          +2     
  Misses           842         842                 
  Partials         107         107                 

Impacted Files	Coverage Δ
clients/object_store_client.go	87.50000% <100.00000%> (+0.35714%)	⬆️

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Impacted Files	Coverage Δ
clients/object_store_client.go	87.50000% <100.00000%> (+0.35714%)	⬆️

[thomshutt]

LGTM other than the couple of minor tweaks I've proposed

[thomshutt]

Also, let's remove that hacky 5 second wait that I put in now that we have a better solution!