tests: don't drop global hgrc
Various tests are failing when the simple store extension is loaded
because the test overrides HGRCPATH and preempts loading of extensions
that were injected via --extra-config-opt.
In most cases, it is acceptable to always load the global HGRCPATH.
So this commit changes a couple of tests so the global HGRCPATH
is still pulled in.
Differential Revision: https://phab.mercurial-scm.org/D3098
Set up
$ hg init repo
$ cd repo
Try to import an empty patch
$ hg import --no-commit - <<EOF
> EOF
applying patch from stdin
abort: stdin: no diffs found
[255]
No dirstate backups are left behind
$ ls .hg/dirstate* | sort
.hg/dirstate