[Cashtab] More improvements to agora partial sale tx parsing

Summary: Patch a bug in how agora txs are parsed so that (edge-case) wallets with multiple paths do not double or tripple-count agora amounts.

Test Plan: npm test

Reviewers: #bitcoin_abc, emack

Reviewed By: #bitcoin_abc, emack

Subscribers: emack

Differential Revision: https://reviews.bitcoinabc.org/D17128