Pointer dgrp is being assigned but is never used hence it is redundant
and can be removed.

Cleans up clang warning:
warning: variable 'dgrp' set but not used [-Wunused-but-set-variable]
Signed-off-by: NColin Ian King <colin.king@canonical.com>
Signed-off-by: NJens Axboe <axboe@kernel.dk>