tests: fix test-clonebundles on recent openbsd
I guess openbsd feels like it needs to stringify this errno in
lowercase and omit the "host" part of "hostname. Okay.
Reported in a big test diff talking about libressl, see 6122. I'm not
flagging this because most of that issue is about a libressl string
change, so this doesn't really make a big difference there.
Differential Revision: https://phab.mercurial-scm.org/D6399