smoke: retry failed upload

[acud]

retries the smoke test upload phase in order to get around the unknown host errors we're seeing:

INFO [11-20|10:30:07.434|swarm-smoke/util.go:77] smoke test starting                      task=upload-and-sync timeout=1000
INFO [11-20|10:30:07.671|swarm-smoke/upload_and_sync.go:282] uploading to http://swarm-private-0.swarm-private-headless:8500 and syncing seed=1574245807434746056
ERROR[11-20|10:30:32.710|swarm-smoke/upload_and_sync.go:288] dial tcp: lookup swarm-private-0.swarm-private-headless on 172.20.0.10:53: no such host 
INFO [11-20|10:30:32.710|swarm-smoke/util.go:73]             total time                               time=25.275515061s kb=100000
ERROR[11-20|10:30:32.756|swarm-smoke/main.go:86]             dial tcp: lookup swarm-private-0.swarm-private-headless on 172.20.0.10:53: no such host