[Bug] `graphman copy list` can fail

Bug report

When the destination (maybe also the source) of a copy operation becomes unused but has not been removed yet, graphman copy list will fail with an error Error: store error: NotFound

The code should take this corner case into account.

Relevant log output

------------------------------------------------------------------------------
deployment           | Qm...
action               | sgd1 -> sgd2 (shardx)
Error: store error: NotFound

Some information to help us out

• Tick this box if this bug is caused by a regression found in the latest release.
• Tick this box if this bug is specific to the hosted service.
• I have searched the issue tracker to make sure this issue is not a duplicate.

OS information

None

Commencez par la commande graphman copy list et reproduisez l’erreur signalée store error: NotFound lorsqu’une destination de copie n’est pas utilisée mais est toujours présente. Suivez la manière dont la commande recherche les stores source et destination, ajoutez une couverture pour ce cas limite et confirmez que la commande répertorie la copie sans échouer.