test: enable sparse-revlog for test-ssh.t
We are about to enable sparse-revlog globally. To help with reviewing the tests
change, we isolate them in individual changesets.
Differential Revision: https://phab.mercurial-scm.org/D5338
#
# Avoid interference from actual test env:
unset HGTEST_JOBS
unset HGTEST_TIMEOUT
unset HGTEST_PORT
unset HGTEST_SHELL