LU-3280 ldlm: suppress useless lock RPC for layout

LU-3280 ldlm: suppress useless lock RPC for layout

In ldlm_lock_decref_internal() when l_lvb_data is freed to
reduce memory consumption, LDLM_FL_LVB_READY is not
cleared, so later when the lock is reused lvb is not
updated. But clearing LDLM_FL_LVB_READY forces layout refetch
at each file access, so the better is to remove the optimization.
The use case is after a restore in HSM.

Signed-off-by: JC Lafoucriere <jacques-charles.lafoucriere@cea.fr>
Change-Id: I3aa56cf39fe34941d227400410b27db32479b1b1
Reviewed-on: http://review.whamcloud.com/6268
Tested-by: Hudson
Reviewed-by: Fan Yong <fan.yong@intel.com>
Tested-by: Maloo <whamcloud.maloo@gmail.com>
Reviewed-by: Andreas Dilger <andreas.dilger@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>