LU-13609 llog: list all the log files correctly on MGS/MDT

"lctl --device xxx llog_catlist" should list all the config log on
MGS and catalog on MDT correctly without any buffer size limit.
If data can't be fetched in one time, data->ioc_count is used to
save the number of all the fetched logs and then continue.

conf-sanity.sh test_123af is added to verify this patch.

Signed-off-by: Emoly Liu <emoly@whamcloud.com>
Change-Id: I364d563446833751b1f017fa2bef0351dab56235
Reviewed-on: https://review.whamcloud.com/38917
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Reviewed-by: Ben Evans <beevans@whamcloud.com>
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>