Targetd Plugin: Add access_group_initiator_delete() support.
Targetd Plugin: Add access_group_initiator_delete() support.

 * Add access_group_initiator_delete() support and raise proper error
   as API document required.

Changes in V2:
 * Add missing capabilities:
    Capabilities.ACCESS_GROUP_INITIATOR_DELETE

 * Add missing @handle_errors decorator to this public method:
    * access_group_initiator_delete()

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

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