staging/lustre/llite: Access to released file triggers a restore

When a client accesses data in a released file,
or truncate it, client must trig a restore request.
During this restore, the client must not glimpse and
must use size from MDT. To bring the "restore is running"
information on the client we add a new t_state bit field
to mdt_info which will be used to carry transient file state.
To memorise this information in the inode we add a new flag
LLIF_FILE_RESTORING.

Intel-bug-id: https://jira.hpdd.intel.com/browse/LU-3432
Lustre-change: http://review.whamcloud.com/6537


Signed-off-by: JC Lafoucriere <jacques-charles.lafoucriere@cea.fr>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>
Tested-by: Oleg Drokin <oleg.drokin@intel.com>
Signed-off-by: Peng Tao <bergwolf@gmail.com>
Signed-off-by: Andreas Dilger <andreas.dilger@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>