tests/helper-runtests.sh

test-subrepo: glob away an unstable hash

This is the instability mentioned at the beginning of the series.  I don't like
hiding it, but I don't want to sit on a fix for a user reported problem while
trying to figure this out.

The instability seems related to the cset with a .hgsub with a remote URL.
(There's very little existing remote URL subrepo testing.)

#
# Avoid interference from actual test env:

unset HGTEST_JOBS
unset HGTEST_TIMEOUT
unset HGTEST_PORT
unset HGTEST_SHELL