tests/helper-runtests.sh

shelve: trust caller of shelvedfile.opener() to check that the file exists

The only place we call `shelvedfile.opener()` is when we're about to
apply a bundle. The file should always exist. If it doesn't, the
`.hg/` directory is corrupt and we don't provide any guarantees about
supporting corrupt repos (besides, telling the user that the shelve
doesn't exist when `hg shelve --list` lists it is not very helpful).

Differential Revision: https://phab.mercurial-scm.org/D9698

#
# Avoid interference from actual test env:

unset HGTEST_JOBS
unset HGTEST_TIMEOUT
unset HGTEST_PORT
unset HGTEST_SHELL