KUDU-2470: retry failed thirdparty downloads
KUDU-2470: retry failed thirdparty downloads

Currently we re-download when we fail to open thirdparty archives that
fail to read. We don't currently re-attempt to download if the download
itself fails. This patch adds the behavior to download failures, using
curl's built-in --retry option that exponentially backs off on failure.

Change-Id: Ia57dd9640d732a75659ca11763d89aefdaf16be1
Reviewed-on: http://gerrit.cloudera.org:8080/10684
Reviewed-by: Adar Dembo <866ca730bfc7f544e3ebce604ceeba4879f23df0@cloudera.com>
Tested-by: Kudu Jenkins

EvilMcJerkface/kudu,cloudera/kudu,cloudera/kudu,EvilMcJerkface/kudu,helifu/kudu,cloudera/kudu,andrwng/kudu,cloudera/kudu,andrwng/kudu,EvilMcJerkface/kudu,helifu/kudu,helifu/kudu,helifu/kudu,andrwng/kudu,InspurUSA/kudu,helifu/kudu,InspurUSA/kudu,cloudera/kudu,andrwng/kudu,andrwng/kudu,EvilMcJerkface/kudu,InspurUSA/kudu,InspurUSA/kudu,EvilMcJerkface/kudu,andrwng/kudu,helifu/kudu,EvilMcJerkface/kudu,cloudera/kudu,EvilMcJerkface/kudu,InspurUSA/kudu,InspurUSA/kudu,helifu/kudu,EvilMcJerkface/kudu,InspurUSA/kudu,andrwng/kudu,andrwng/kudu,cloudera/kudu,helifu/kudu,andrwng/kudu,helifu/kudu,cloudera/kudu,InspurUSA/kudu,InspurUSA/kudu,EvilMcJerkface/kudu,cloudera/kudu