LU-17025 llapi: Verify stripe pool name

LU-17025 llapi: Verify stripe pool name

Verify the pool exists when setting a stripe within a pool.
This avoids situations where the user specifies a missing
or invalid pool and an invalid stripe is created

test changes: Ensure pool exist before use

ost-pools.sh:
the test_6 test_7c and test_32 created pool before
calling setstripe -p

sanity-pfl.sh:
test_14 created pool before using it

sanity-flr.sh:
Test test_0b, test_0c, test_0e and test_0f
modified to create pool before using it

Test-parameters: trivial testlist=ost-pools,sanity-pfl,sanity-flr
HPE-bug-id: LUS-11510
Fixes: cd1f8527d414 ("LU-14645 utils: optimise setstripe")
Signed-off-by: Rajeev Mishra <rajeevm@hpe.com>
Change-Id: I146bc6f886cd083b318dc9ea2e5d1943955bd7d6
Reviewed-on: https://review.whamcloud.com/c/fs/lustre-release/+/51963
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Shaun Tancheff <shaun.tancheff@hpe.com>
Reviewed-by: Petros Koutoupis <petros.koutoupis@hpe.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>