ONTAP Plugin: Add support of Disk.STATUS_FREE
ONTAP Plugin: Add support of Disk.STATUS_FREE

 * Any disk not have 'aggregate' property is considered as free disk.

 * Added comments indicate how spare and free disk works on ONTAP:
    1. Spare  == free disk
    2. Zeroed spare disk == OK | SPARE | FREE
    3. Non-zeroed spare disk == STOPPED | SPARE | FREE

Changes in V2:
 * Should not mark partner filer's disks as free.
   # Don't check status of partner's disks, simply mark as STATUS_OTHER.

Signed-off-by: Gris Ge <e24f3acbe39bf94f92e8af3c48f8852106ad5ad7@redhat.com>

jumitche/libstoragemgmt,joehandzik/libstoragemgmt,HP-Scale-out-Storage/libstoragemgmt,jumitche/libstoragemgmt,jumitche/libstoragemgmt,libstorage/libstoragemgmt,tasleson/libstoragemgmt,joehandzik/libstoragemgmt,tasleson/libstoragemgmt,tasleson/libstoragemgmt,lazy404/libstoragemgmt,cathay4t/libstoragemgmt,cathay4t/libstoragemgmt,libstorage/libstoragemgmt,tasleson/libstoragemgmt,libstorage/libstoragemgmt,cathay4t/libstoragemgmt,cathay4t/libstoragemgmt,HP-Scale-out-Storage/libstoragemgmt,libstorage/libstoragemgmt,cathay4t/libstoragemgmt,lazy404/libstoragemgmt,tasleson/libstoragemgmt,lazy404/libstoragemgmt,HP-Scale-out-Storage/libstoragemgmt,libstorage/libstoragemgmt,jumitche/libstoragemgmt,HP-Scale-out-Storage/libstoragemgmt,joehandzik/libstoragemgmt,lazy404/libstoragemgmt,jumitche/libstoragemgmt,joehandzik/libstoragemgmt