LU-5218 llog: keep llog ctxt indices constant

The llog context id table cannot be shrinked easily because that
will cause index shifting and incompatibility between old client
and new server and vice versa.

Patch moves llog_ctxt_id table to the lustre_idl.h because this is
wire protocol data, these values are added to the wirecheck and
checks are added in llog server code for wire data.

Signed-off-by: Mikhail Pershin <mike.pershin@intel.com>
Change-Id: I003120223504d95164e4392b01c096e3e8b0fef0
Reviewed-on: http://review.whamcloud.com/10758
Reviewed-by: Andreas Dilger <andreas.dilger@intel.com>
Tested-by: Jenkins
Tested-by: Oleg Drokin <oleg.drokin@intel.com>
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>