vine: resolve uncertain temp availability issue

[colinthomas-z80]

Proposed changes

Begin with a check to make sure a replica is ready to transfer when we decide the file is available

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Additional comments

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[colinthomas-z80]

#3692

[btovar]

This is a step in the right direction, however it may hide a root cause. When the manager stopped scheduling there were no tasks running, therefore there were no tasks running. Further, I waited for about 15min, so any transfer would have completed by then. Thus, either the replica had a pending state which will never progress to ready, or it is already ready and can't be found.

Could it be that this is related to #3695 where a replica in the pending state is never removed after an invalid message?

[btovar]

ready to merge?