LU-8911 tests: sanity-hsm test_24d fails on a local setup

In test_24d, do not use the default mountpoint of copytool_setup()
as it is also the one the test mounts in read-only mode.

This patch also removes:
 - the "continuing fast path" in copytool_setup (calling
   "pkill -CONT -x lhsmtool_posix" instead of launching a new
   copytool) as it is not explicitly used by any test
 - as well as the first copytool_setup located outside of any
   tests.

Test-Parameters: trivial testlist=sanity-hsm
Signed-off-by: Quentin Bouget <quentin.bouget@cea.fr>
Change-Id: I86bc41213bc656d7a83d63fb8e9bc595ba6b73ca
Reviewed-on: https://review.whamcloud.com/24185
Reviewed-by: Faccini Bruno <bruno.faccini@intel.com>
Tested-by: Jenkins
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: Dmitry Eremin <dmitry.eremin@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>