Merge #10294: [Wallet] unset change position when there is no change

Summary:
7c58863 [Wallet] unset change position when there is no change on exact match (Gregory Sanders)

Tree-SHA512: ce8b9337e4132e32d80f954258d50938052c833a48e39431649d6adb16e3d18626a0ae5d300827e7fa397927fba72a1f066cb31af9b0a3ef7f1feb6024461626

Backport of Core PR10294
https://github.com/bitcoin/bitcoin/pull/10294/files
Completes T535

Test Plan:

make check
test_runner.py rpc_fundrawtransaction

Reviewers: deadalnix, Fabien, #bitcoin_abc

Reviewed By: deadalnix, #bitcoin_abc

Subscribers: teamcity, schancel

Differential Revision: https://reviews.bitcoinabc.org/D2502