4651: Accept "false" as false for a boolean param. Reject bogus strings.

Also, advertise find_or_create param from the controller, not just the
discovery document generator.
4651: Fix KeepDisksController test failures.
4651: Update NodesController _ping_requires_parameters format.
4651: Merge branch 'master' into 4651-boolean-params
4651: ensure_unique_name param is not required.
4651: Fix exceptions. Accept 0 for false, 1 for true.
Merge branch '4651-boolean-params' closes #4651
Update arvados-cli Gemfile.lock. No issue #