[tasks] implement exponential backoff

This is to avoid bombarding users with task errors.
2 jobs for 565-dev-ngrams-table-click-on-child in 0 seconds (queued for 107 minutes and 23 seconds)
Status Job ID Name Coverage
  Test
failed #7564
deps

failed #7565
test

 
Name Stage Failure
failed
test Test There has been a timeout failure or the job got stuck. Check your timeout limits or try again
No job trace
failed
deps Test There has been a timeout failure or the job got stuck. Check your timeout limits or try again
No job trace