Make `repack --justaddcopies` possible in ACTIVE tapes

Problem

The command cta-admin repack add --vid <vid> --justaddcopies makes no changes to the tape <vid>, but still requires it to be in REPACKING state.

There is no practical reason for this restriction, but doing it results in the tape <vid> being temporarily unavailable for user retrieves.

Suggestion

Make it possible to trigger --justaddcopies in ACTIVE tapes.

The amount of work required to implement this feature needs to be evaluated. Since --justaddcopies is deeply tied to the repack workflow, separating it may require a lot of extra work.

Task:

• Evaluate the feasibility of making "repack" --justaddcopies possible on tapes on user domain.