LU-3806 obdclass: add LCT_SERVER_SESSION for server session

LU-3806 obdclass: add LCT_SERVER_SESSION for server session

Add LCT_SERVER_SESSION for server session, and separate the
server session flag from LCT_SESSION, so to avoid allocating
session info for client stack for each server request, if
client and server are on the same node.

Signed-off-by: Wang Di <di.wang@intel.com>
Change-Id: I808c3f58cd7a03ebc166e51fe1e32ea34ae0e3e8
Reviewed-on: http://review.whamcloud.com/7412
Reviewed-by: John L. Hammond <john.hammond@intel.com>
Tested-by: Hudson
Tested-by: Maloo <whamcloud.maloo@gmail.com>
Reviewed-by: Mike Pershin <mike.pershin@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>