fix: prevent some checks when using session key

[SgtPooki]

When calling checkUploadReadiness with a filecoin-pin session key, it should not try to configure allowances.

Note: we need to make this more robust for the future, and should add helpers for consumers and authorization checks of the session key, because some session keys might have varying permissions.

cc @rvagg

related to #101 we likely need to fix logic because if allowances are set we shouldn't need to set them again

[wjmelements]

unused?

[SgtPooki]

Forgot to remove leftover.. My bad

[SgtPooki]

#111

[rvagg]

@SgtPooki what do you think about user feedback in this case? Maybe there's some explicit early-failures we should make in cases we don't want to support, like --auto-fund with a session key. But I'm also concerned about the case where they really do need allowances set up properly and their operation is going to fail because their wallet just isn't ready—we should be able to catch that and fail early with a sensible message rather than having an unhelpful revert show up. Maybe we should extend the return type(s) here to say "something needs to be done but I couldn't do it cause it's a session key"? Thoughts?