Merge #10816: Properly forbid -salvagewallet and -zapwallettxes for multi wallet.
Summary: PR10816 backport ; fixes misbackport in D1061
Test Plan: ninja check-all
Reviewers: #bitcoin_abc, Fabien
Reviewed By: #bitcoin_abc, Fabien
Differential Revision: https://reviews.bitcoinabc.org/D5261