LU-17224 tests: improve OST out-of-space testing

LU-17224 tests: improve OST out-of-space testing

Add file system reservation with fallocate
to reduce I/O size with dd command

Test-Parameters: trivial testlist=sanityn env=MAXFREE=60000000
Signed-off-by: Vikentsi Lapa <vlapa@whamcloud.com>
Change-Id: I40b64c1825aa5067788b6b31902d282ba59ccd13
Reviewed-on: https://review.whamcloud.com/c/fs/lustre-release/+/57260
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Reviewed-by: Rajeev Mishra <rajeevm@hpe.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>