LU-15171 osd-ldiskfs: xattr_sem locking is missing for dquot_transfer

LU-15171 osd-ldiskfs: xattr_sem locking is missing for dquot_transfer

Kernel commit 7a9ca53ae (~v4.13) added the requirement for xattr_sem locking
when calling *dquot_transfer. As of now, in rare cases, it is possible that
we can modify inode xattrs and perform their consistency checks in parallel,
which can fail.

Change-Id: I041694e30ce6c8398864c0ad57671df0bffd2f52
Signed-off-by: Andrew Perepechko <andrew.perepechko@hpe.com>
HPE-bug-id: LUS-10549
Reviewed-on: https://review.whamcloud.com/45424
Reviewed-by: Alexander Zarochentsev <alexander.zarochentsev@hpe.com>
Tested-by: jenkins <devops@whamcloud.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>