Allow `:manager_ref` and `:manager_ref_allowed_nil` to be passed as a singular value

[agrare]

The 90% case is that these are a single column (e.g. :ems_ref or :uid_ems) so allow the user to pass in a single value and wrap it in an array when building the collection.

[miq-bot]

This issue has been automatically marked as stale because it has not been updated for at least 6 months.

If you can still reproduce this issue on the current release or on master, please reply with all of the information you have about it in order to keep the issue open.

Thank you for all your contributions!

[miq-bot]

This issue has been automatically marked as stale because it has not been updated for at least 3 months.

If you can still reproduce this issue on the current release or on master, please reply with all of the information you have about it in order to keep the issue open.

Thank you for all your contributions! More information about the ManageIQ triage process can be found in the traige process documentation.