[PATCH 2 of 2 STABLE] test-obsmarker-template: run mkcommit in subshell to isolate envvars

[Augie Fackler]

> On Jul 28, 2018, at 03:03, Yuya Nishihara <yuya at tcha.org> wrote:
> 
> # HG changeset patch
> # User Yuya Nishihara <yuya at tcha.org>
> # Date 1532760723 -32400
> #      Sat Jul 28 15:52:03 2018 +0900
> # Branch stable
> # Node ID 5b3b74e4b21442777f741df60fd81e52e220a182
> # Parent  2b7ce7b55514e248a3247f135f1938090ff19045
> test-obsmarker-template: run mkcommit in subshell to isolate envvars
> 
> I don't know if it is a feature or a bug, but it appears that environment
> variables passed to a shell function persist on /bin/sh.

Wow. I spent a while trying to figure this failure on the BSD buildbot out and got stumped. Nice find!