_data.py: Make _check_opt_data class method
_data.py: Make _check_opt_data class method

The method was already very close to being a method,
so moved it and removed the allowed parameter to
reference the class as it already was.

Signed-off-by: Tony Asleson <1ef2d381aa56d512126ddaacc29e68136e4fdf55@redhat.com>

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