LU-15104 tests: create client dirs with custom stripe count

LU-15104 tests: create client dirs with custom stripe count

Random ha_dir_stripe_count allows clients to create directories
with different stripe counts in one ha.sh test session.
Please use
  DSTRIPECOUNT=3 DSTRIPECOUNTRAND=true
to create the directories with stripe counts 1,2 or 3.

Test-Parameters: trivial
Signed-off-by: Elena Gryaznova <elena.gryaznova@hpe.com>
HPE-bug-id: LUS-10435
Reviewed-by: Vladimir Saveliev <vlaidimir.saveliev@hpe.com>
Reviewed-by: Andriy Skulysh <andriy.skulysh@hpe.com>
Change-Id: I0092958a9bcf1991adc9f45ac1fbed9340a06c57
Reviewed-on: https://review.whamcloud.com/45240
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>