HDDS-3164. Add Recon endpoint to serve missing containers and its metadata.

[vivekratnavel]

What changes were proposed in this pull request?

• Add an endpoint (/api/v1/containers/missing) to serve missing containers response
• Add unit tests

What is the link to the Apache JIRA

https://issues.apache.org/jira/browse/HDDS-3164

How was this patch tested?

• Unit test
• Manual test:
  • Bring ozone via docker compose
  • Add random keys with RATIS factor ONE using freon (ozone freon rk --replicationType=RATIS --numOfVolumes=10 --numOfBuckets=10 --numOfKeys=10 --factor=ONE --numOfThreads=20)
  • Bring down one datanode
  • After 10m, the datanode should be reported as dead in Recon and the next run of MissingContainerTask should catch the missing containers in the dead datanode.

[vivekratnavel]

@avijayanhwx @elek Please review

[avijayanhwx]

Changes look good to me. Minor comments inline.

[vivekratnavel]

Acceptance test failure is not related to the change. It fails due to no space available on disk

Failing this attempt.Diagnostics: [2020-03-25 11:34:00.461]No space available in any of the local directories.

[avijayanhwx]

Thank you for the contribution @vivekratnavel.

[elek]

If you see a flaky test, please disable it (without and issue) + create a new open issue and repeat the build. There is some risk that one flakiness hides a other. Merging patches without green build makes harder to debug flaky tests.