tests: make the commands.resolve.confirm tests not pollute the test-wide hgrc

Authored by spectral.

Description

tests: make the commands.resolve.confirm tests not pollute the test-wide hgrc

I want to add tests after these tests that create a new repo and use it, and was
confused for a bit as to why they were seeing different behavior than I
expected.

Differential Revision: https://phab.mercurial-scm.org/D5242