Add more robust check for locked wallet

[JVillella]

I've been testing the latest LND w/ Umbra and have found it is doesn't try to unlock the wallet due to a faulty is locked check. This should be more robust from looking at the LND code.

[AaronDewes]

Thanks a lot, @JVillella! Have you sucessfully tested this?

[JVillella]

Yep, been running locally for a few days now.

[lukechilds]

Thanks so much for this @JVillell!

So this isn't an immediate issue but will effect LND v0.13.0 once released, right?

[JVillella]

It's a fix needed for LND 0.13, that's right - but it's backwards compatible.

[AaronDewes]

1. We probably don't need compatibility with older LND versions, once we release Umbrel with LND 0.13, this PR can be merged at the same time.

2. This is not the recommended way of checking if LND is unlocked:

[JVillella]

1. I would recommend backwards compatibility. Not everyone is going to update their lnd docker node in their compose file.
2. Nice to know they have a new service; I was following their approach internally but looks like there are better ways to do this now. I won't have time to make these changes, so feel free to replace this PR or add to it with what's required.

[AaronDewes]

Not everyone is going to update their lnd docker node in their compose file.

To not do that, they would need to fork/modify Umbrel, which Umbrel doesn't need to care about in my opinion.