LU-12704 lov: check all entries in lov_flush_composite

LU-12704 lov: check all entries in lov_flush_composite

Check all layout entries for DOM layout and exit with
-ENODATA if no one exists. Caller consider that as valid
case due to layout change.

Define llo_flush methods for all layouts as required
by lov_dispatch().

Patch cleans up also cl_dom_size field in cl_layout which
was used in previous ll_dom_lock_cancel() implementation

Run lov_flush_composite under down_read lov->lo_type_guard to avoid
race with layout change.

Fixes: 707bab62f5 ("LU-12296 llite: improve ll_dom_lock_cancel")

Test-Parameters testlist=racer
Signed-off-by: Mikhail Pershin <mpershin@whamcloud.com>
Signed-off-by: Vladimir Saveliev <c17830@cray.com>
Change-Id: I4e7b1b201bb1a669fe0d8f0f728467e579ef3512
Reviewed-on: https://review.whamcloud.com/36368
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>