LU-14755 tests: create custom pools

LU-14755 tests: create custom pools

We are interested in running some tests on fs with
the pools. The proposed enhancement allows to create
$FS_NPOOLS number of pools containing $FS_POOL_NOSTS
number of osts. If $FS_NPOOLS not set the number of
pools created is $OSTCOUNT / $FS_POOL_NOSTS.
Pools names are $FS_POOL based. Pools are not created if
FS_POOL not set.
Examples 1:
  FS_POOL=global OSTCOUNT=2
lustre.global0
OST lustre-OST0000_UUID
OST lustre-OST0001_UUID
Example 2:
  FS_POOL=global OSTCOUNT=6 FS_POOL_NOSTS=3
lustre.global0
OST lustre-OST0000_UUID
OST lustre-OST0001_UUID
OST lustre-OST0002_UUID
lustre.global1
OST lustre-OST0003_UUID
OST lustre-OST0004_UUID
OST lustre-OST0005_UUID
Example 3:
  FS_POOL=p OSTCOUNT=5 KEEP_POOLS=true FS_NPOOLS=7 FS_POOL_NOSTS=3
Pool: lustre.p0
lustre-OST0000_UUID
lustre-OST0001_UUID
lustre-OST0002_UUID
Pool: lustre.p1
lustre-OST0003_UUID
lustre-OST0004_UUID
lustre-OST0000_UUID
Pool: lustre.p2
lustre-OST0001_UUID
lustre-OST0002_UUID
lustre-OST0003_UUID
Pool: lustre.p3
lustre-OST0004_UUID
lustre-OST0000_UUID
lustre-OST0001_UUID
Pool: lustre.p4
lustre-OST0002_UUID
lustre-OST0003_UUID
lustre-OST0004_UUID
Pool: lustre.p5
lustre-OST0000_UUID
lustre-OST0001_UUID
lustre-OST0002_UUID
Pool: lustre.p6
lustre-OST0003_UUID
lustre-OST0004_UUID
lustre-OST0000_UUID

Patch adds the ability to remove all old pools at the
start if DELETE_OLD_POOLS set to true (default is false)
and the ability keep the new pools not deleted at the
end if KEEP_POOLS set to true (default is false).

Test-Parameters: trivial testlist=sanity-flr,ost-pools,ost-pools,sanity-pfl,sanity,sanityn
Signed-off-by: Elena Gryaznova <elena.gryaznova@hpe.com>
HPE-bug-id: LUS-8172
Reviewed-by: Sergey Cheremencev <sergey.cheremencev@hpe.com>
Reviewed-by: Vladimir Saveliev <vladimir.saveliev@hpe.com>
Change-Id: I73b72f9f39933b5b875978ce4fede5e9828c4c71
Reviewed-on: https://review.whamcloud.com/43966
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Vladimir Saveliev <vlaidimir.saveliev@hpe.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>