LU-7273 tests: dump stacks upon CT stop failure

LU-7273 tests: dump stacks upon CT stop failure

This patch adds full threads stacks dump upon copytool stop failure
at end of grace period, in sanity-hsm/wait_copytools().

Signed-off-by: Bruno Faccini <bruno.faccini@intel.com>
Change-Id: I3da4876b55fbc72c941bbf75cc89819acecc82c0
Reviewed-on: http://review.whamcloud.com/16782
Tested-by: Jenkins
Reviewed-by: Jian Yu <jian.yu@intel.com>
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: John L. Hammond <john.hammond@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>