LU-13636 osd: create agent inode with explicit owner

LU-13636 osd: create agent inode with explicit owner

to avoid quota misaccounting.

Test-Parameters: fstype=ldiskfs
Signed-off-by: Alex Zhuravlev <bzzz@whamcloud.com>
Change-Id: I5a02e6e7de71821a10704ac3516ee087998c9c21
Reviewed-on: https://review.whamcloud.com/38842
Reviewed-by: Hongchao Zhang <hongchao@whamcloud.com>
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>