FSAL_LUSTRE: use fsal_filesystem lib to manage FSAL_LUSTRE.
FSAL_LUSTRE/fsal_filesystem: adds lustre_alloc_handle()
FSAL_LUSTRE/fsal_file_system : adds lustre_extract_fsid()
FSAL_LUSTRE: adds fsdev to fsal_handle to avoid collision in cache_inode

/!\  THIS IS A WIP COMMIT, do not merge upstream !!!

/!\ this commit compiles, but work is to be done to handle "lustre-extract_fsid" correctly.
It should not be run by now.

Signed-off-by: Philippe DENIEL <philippe.deniel@cea.fr>