LU-13411 llog: allow delete of zero size llog

LU-13411 llog: allow delete of zero size llog

1) all plain logs belonging to catalog should have flag
LLOG_F_ZAP_WHEN_EMPTY base on llog_cat_new_log(). When
llog_cat_process_common processing plain log with zero file size,
this flag is not set during llog_cat_id2handle LLOG_EMPTY, so these
plain llogs are not canceled/destroyed. They appeared during cross
MDT updates. Fix adds flag LLOG_F_ZAP_WHEN_EMPTY for any plain llog
at catalog.

Signed-off-by: Alexander Boyko <c17825@cray.com>
Cray-bug-id: LUS-8634
Change-Id: Ieebee67bf9e7bebb9ecc51b858a9976a00583c7b
Reviewed-on: https://review.whamcloud.com/38131
Reviewed-by: Mike Pershin <mpershin@whamcloud.com>
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Alexander Zarochentsev <alexander.zarochentsev@hpe.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>