LU-1302 mgs: mgs uses llog over OSD

LU-1302 mgs: mgs uses llog over OSD

- llog over OSD in MGS. Switch llog_test to work over OSD too.
- local_oid_store_init() don't create names for llog because all
  llogs have names in O/d/n
- Enable all llog tests functionality

Signed-off-by: Mikhail Pershin <tappro@whamcloud.com>
Change-Id: I60cc5ec7094a2640d7fc0a0d87519c56b1383557
Reviewed-on: http://review.whamcloud.com/4104
Tested-by: Hudson
Reviewed-by: Alex Zhuravlev <bzzz@whamcloud.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Tested-by: Maloo <whamcloud.maloo@gmail.com>