bots: Fix race in pruning the GitHub cache
bots: Fix race in pruning the GitHub cache

When two bots end up pruning the GitHub cache at the same
time it can come to races on the os.remove() command.

Lets ignore these, and just have the pruning pick up next
time around.

Closes #6609

dperpeet/cockpit,michalskrivanek/cockpit,andreasn/cockpit,mvollmer/cockpit,xhad/cockpit,xhad/cockpit,larsu/cockpit,stefwalter/cockpit,dperpeet/cockpit,michalskrivanek/cockpit,xhad/cockpit,moraleslazaro/cockpit,mareklibra/cockpit,xhad/cockpit,Scribery/cockpit,larsu/cockpit,harishanand95/cockpit,garrett/cockpit,mareklibra/cockpit,SotolitoLabs/cockpit,deryni/cockpit,cockpit-project/cockpit,stefwalter/cockpit,cockpituous/cockpit,stefwalter/cockpit,Scribery/cockpit,deryni/cockpit,stefwalter/cockpit,mareklibra/cockpit,SotolitoLabs/cockpit,larskarlitski/cockpit,cockpituous/cockpit,larskarlitski/cockpit,moraleslazaro/cockpit,petervo/cockpit,stefwalter/cockpit,mvollmer/cockpit,mvollmer/cockpit,moraleslazaro/cockpit,martinpitt/cockpit,moraleslazaro/cockpit,larskarlitski/cockpit,dperpeet/cockpit,michalskrivanek/cockpit,cockpit-project/cockpit,michalskrivanek/cockpit,martinpitt/cockpit,SotolitoLabs/cockpit,moraleslazaro/cockpit,martinpitt/cockpit,mareklibra/cockpit,cockpituous/cockpit,deryni/cockpit,Scribery/cockpit,Scribery/cockpit,andreasn/cockpit,larskarlitski/cockpit,dperpeet/cockpit,harishanand95/cockpit,mvollmer/cockpit,michalskrivanek/cockpit,larsu/cockpit,harishanand95/cockpit,mareklibra/cockpit,cockpituous/cockpit,harishanand95/cockpit,garrett/cockpit,larskarlitski/cockpit,andreasn/cockpit,garrett/cockpit,andreasn/cockpit,andreasn/cockpit,cockpit-project/cockpit,michalskrivanek/cockpit,SotolitoLabs/cockpit,larsu/cockpit,mareklibra/cockpit,garrett/cockpit,larskarlitski/cockpit,cockpituous/cockpit,petervo/cockpit,martinpitt/cockpit,xhad/cockpit,cockpit-project/cockpit,Scribery/cockpit,deryni/cockpit,cockpit-project/cockpit,moraleslazaro/cockpit,larsu/cockpit,andreasn/cockpit,stefwalter/cockpit,petervo/cockpit,petervo/cockpit,deryni/cockpit,michalskrivanek/cockpit,xhad/cockpit,Scribery/cockpit,SotolitoLabs/cockpit,larskarlitski/cockpit,martinpitt/cockpit,garrett/cockpit,petervo/cockpit,stefwalter/cockpit,andreasn/cockpit,harishanand95/cockpit,dperpeet/cockpit,SotolitoLabs/cockpit,mvollmer/cockpit,Scribery/cockpit,dperpeet/cockpit,dperpeet/cockpit,petervo/cockpit,harishanand95/cockpit,xhad/cockpit,cockpituous/cockpit,deryni/cockpit,petervo/cockpit,harishanand95/cockpit,deryni/cockpit,mareklibra/cockpit,larsu/cockpit,moraleslazaro/cockpit,SotolitoLabs/cockpit