LU-1330 obdclass: add obd_target.h

Move some server-side data structures form obd.h to obd_target.h.  To
remove some code dependencies use HAVE_SERVER_SUPPORT to protect some
llog/fsfilt_* functions.

Signed-off-by: Liu Xuezhao <xuezhao.liu@emc.com>
Signed-off-by: John L. Hammond <john.hammond@intel.com>
Change-Id: I4e79f76220cc194c31ca4005ff6286a4a6bd72e9
Reviewed-on: http://review.whamcloud.com/2678
Tested-by: Hudson
Tested-by: Maloo <whamcloud.maloo@gmail.com>
Reviewed-by: Andreas Dilger <andreas.dilger@intel.com>
Reviewed-by: Peng Tao <bergwolf@gmail.com>
Reviewed-by: Mike Pershin <mike.pershin@intel.com>