Browser-laptop: ledger persists newClient but restores it to newClient.state

[evq]

Test plan

https://github.com/brave/browser-laptop/pull/11495#issuecomment-336361446

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aka yo dawg I heard you lik state

This issue can lead to an unlimited wait while performing conversion from BTC->BAT. We should be persisting newClient.state instead essentially. We will need some recovery logic to rescue improperly persisted state files.

This issue was originally noted in - https://github.com/brave/browser-laptop/pull/11495

It was marked as a bat-client issue, but I've closed that issue since it is actually due to browser-laptop persistence of the client - https://github.com/brave-intl/bat-client/issues/18

[kjozwiak]

@evq should we put this into 0.19.x Hotfix 2 since the milestone will mostly concentrate on ledger/payment fixes/improvements? I'm not 100% sure when 0.19.x Hotfix 2 is slated for, but if we don't have time, we should stick this into 0.19.x Hotfix 3.

[evq]

Yes, let's target 0.19.x Hotfix 2

[kjozwiak]

@evq are the STR in https://github.com/brave/browser-laptop/pull/11495#issuecomment-336361446 sufficient for this issue/case?

[evq]

@kjozwiak yes, those steps are sufficient - I was able to reproduce using them

[kjozwiak]

Test Case to be used: https://github.com/brave/browser-laptop/pull/11495#issuecomment-336361446