LU-13366 lod: check for extension size at instantiation time

LU-13366 lod: check for extension size at instantiation time

lod_statfs_and_check() may consider an OST as OK, but SEL needs its
extension size to fit the free space and the OST may turn out to be
low-on-space, thus inappropriate OST may be chosen, SEL cannot use
it and ENOSPC occurs.

Take the extension size into account at the object allocation time.
If none of OSTs is able to allocate an object, try to allocate in old
manner instead of returning ENOSPC from lod_qos_prep_create().

Adjust tests to work on smaller extension sizes to fit into OSTs
used for sanity tests to enable the new logic above.

Signed-off-by: Vitaly Fertman <c17818@cray.com>
Change-Id: If5159200a72a68a7261aa7031e58a1ac6a8e3f24
Reviewed-by: Alexey Lyashkov <c17817@cray.com>
Reviewed-by: Andriy Skulysh <c17819@cray.com>
Tested-by: Elena Gryaznova <c17455@cray.com>
Reviewed-on: https://es-gerrit.dev.cray.com/156372
HPE-bug-id: LUS-8157
Reviewed-on: https://review.whamcloud.com/37961
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Alexey Lyashkov <alexey.lyashkov@hpe.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>