update create_wallet for 0.21

[jharveyb]

0.21 added descriptor wallets + the ability to mark wallets for loading on startup.

Descriptor wallets have no "keypool_oldest" parameter, and also never have an HD seed.

Test passed with a node built with descriptor support; I suppose the node used for CI would also need to be built with descriptor support.

[sgeisler]

I actually don't think CI failure is a problem with the node we use for testing, it's rather two-fold:

• your code does not comply with the formatting standards enforced using rustfmt (see the stable run)
• we currently have a problem with rust 1.29.0, presumably because a dependency broke MSRV in a minor version 😦 (see the 1.29.0 run) we'll have to look into this and probably fix it by pinning yet another dependency for 1.29.0 testing.

[sgeisler]

I fixed the 1.29.0 CI in #175. Once it's merged can you please rebase on master? I'll try to get it in quickly, sorry for the inconvenience.

[stevenroose]

looks good, thanks! like Sebastian said, please rebase :)

[sgeisler]

utACK 064b923