Improve "dockerctl check"

- Make number of check retries configurable.
- Exit with "1" exit code if one or more containers failed to pass
  tests.

Change-Id: Ic06eb53efb8fd4b728f87ef3205638eb05742490
Related-bug: #1390129
(cherry picked from commit 593848cd376ba9b9012dfabf48badbeddabbd79e)
Merge "Improve "dockerctl check"" into stable/5.1