LU-4751 hsm: Fix sanity-hsm tests for non-mrsh $PDSH

LU-4751 hsm: Fix sanity-hsm tests for non-mrsh $PDSH

The workaround for starting backgrounded copytool
monitors via pdsh -Rmrsh is not compatible with non-mrsh
values of $PDSH. This commit adds a branch such that
the workaround is only used when required by the test
cluster environment.

Signed-off-by: Michael MacDonald <michael.macdonald@intel.com>
Change-Id: I35a57d26a3836cfd1bbb698d267a8fe9f31f86c8
Reviewed-on: http://review.whamcloud.com/9587
Tested-by: Jenkins
Reviewed-by: James Nunez <james.a.nunez@intel.com>
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: Bob Glossman <bob.glossman@intel.com>
Reviewed-by: John L. Hammond <john.hammond@intel.com>
Reviewed-by: Jian Yu <jian.yu@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>