For RefreshAuthorizedProjectsService, reset the user only after obtaining the lease

What does this MR do?

This change originates from the discussion at https://gitlab.com/gitlab-org/gitlab/-/issues/332120#note_589576340 (confidential)

For a service/worker that performs the work only after obtaining a lease, another instance of the same service/worker could have modified the object and its associations while this one was waiting for obtaining the lease.

So, if we .reset the object before obtaining the lease, it will not be aware of the changes that happened to it, while it was waiting for obtaining the lease.

Logically, it makes sense to .reset the object after obtaining the lease. This way, the object becomes aware of whatever changes that happened to it in the meantime, in a different instance of the same service/worker.

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