LU-3432 llite: Access to released file trigs 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.

Signed-off-by: JC Lafoucriere <jacques-charles.lafoucriere@cea.fr>
Change-Id: I4f3cde9cb247760075f6872b1d1c299ef369a7ae
Reviewed-on: http://review.whamcloud.com/6537
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>
Tested-by: Oleg Drokin <oleg.drokin@intel.com>