Targetd Plugin: Add new targetd API support for volume mask.
Targetd Plugin: Add new targetd API support for volume mask.

 * Changed _search_lsm_ag_by_name() to _lsm_ag_of_id() which now support
   handling fake access group and true access group.
 * Add _lsm_vol_of_id() for validating volume existence.

 * Updated these public methods to support new targetd API:
    * volume_mask()
    * volume_unmask()
    * access_groups_granted_to_volume()
    * volumes_accessible_by_access_group()

Changes in V2:

 * Check access group support status before call out 'access_group_map_list'
   in _tgt_masks() method.

 * Add missing @handle_errors decorator to these public methods:
    * volume_mask()

 * PEP8 fix.

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

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