btrfs-progs: let callers of btrfs_show_qgroups free the buffers

btrfs_show_qgroups frees the filter and comparer in case it succeeds.
This makes the caller slightly more complicated so move the freeing up
one level.

Issue: #20
Signed-off-by: David Sterba <dsterba@suse.com>

cmds-qgroup.c

@@ -396,6 +396,8 @@ static int cmd_qgroup_show(int argc, char **argv)
 	}
 	ret = btrfs_show_qgroups(fd, filter_set, comparer_set);
 	close_file_or_dir(fd, dirstream);
+	free(filter_set);
+	free(comparer_set);
 
 out:
 	return !!ret;

qgroup.c

@@ -1192,8 +1192,6 @@ int btrfs_show_qgroups(int fd,
 	print_all_qgroups(&sort_tree);
 
 	__free_all_qgroups(&qgroup_lookup);
-	free(filter_set);
-	free(comp_set);
 	return ret;
 }