lustre/ptlrpc: skip rpcs that fail ptl_send_rpc

ptl_send_rpc is not dealing with -ENOMEM in some
situations.  When the ptl_send_rpc fails we need
set error and skip further processing or trigger
and LBUG

Signed-off-by: Keith Mannthey <keith.mannthey@intel.com>
Signed-off-by: Peng Tao <bergwolf@gmail.com>
Reviewed-on: http://review.whamcloud.com/7411
Intel-bug-id: https://jira.hpdd.intel.com/browse/LU-3698


Reviewed-by: Mike Pershin <mike.pershin@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>
Signed-off-by: Oleg Drokin <oleg.drokin@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>