Only run UpgradeWallet if the wallet needs to be upgraded

Summary:
Backport of Core PR15761 [2/6] : https://github.com/bitcoin/bitcoin/pull/15761/commits/183323712398e26ddcf3a9dc048aaa9900a91f5a

Depends on D7922

Test Plan:

ninja all check-all

Reviewers: #bitcoin_abc, Fabien

Reviewed By: #bitcoin_abc, Fabien

Differential Revision: https://reviews.bitcoinabc.org/D7923