LU-13064 sec: check permissions for changelogs access

LU-13064 sec: check permissions for changelogs access

root permissions should be checked when reading or clearing changelogs
from clients. In particular, if root is squashed via a nodemap entry,
it should not be allowed to access changelogs.
To achieve this send mdt body along with RQF_LLOG_ORIGIN_HANDLE_CREATE
and RQF_MDT_SET_INFO requests. And on server side, retrieve user
credentials and make sure they have root permission.

Test-Parameters: clientversion=2.12 envdefinitions=SANITY_EXCEPT="27M 56ra 151 156 802"
Test-Parameters: serverversion=2.12
Signed-off-by: Sebastien Buisson <sbuisson@ddn.com>
Change-Id: I0c6cc99f8a7c5a13c2b31009d73f38976931ec37
Reviewed-on: https://review.whamcloud.com/36990
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Reviewed-by: Emoly Liu <emoly@whamcloud.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>