btrfs-progs: qgroup: don't return 1 if qgroup is marked inconsistent during relationship assignment

BTRFS_IOC_QGROUP_ASSIGN ioctl could return >0 if qgroup is marked
inconsistent after successful relationship assignment/removal.

We leak the return value as the final return value of btrfs command.
But according to the man page, return value other than 0 means failure.

Fix this by resetting the return value to 0 for --no-rescan case.

Signed-off-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

cmds-qgroup.c

@@ -123,6 +123,7 @@ static int _cmd_qgroup_assign(int assign, int argc, char **argv,
 				error("quota rescan failed: %m");
 		} else {
 			warning("quotas may be inconsistent, rescan needed");
+			ret = 0;
 		}
 	}
 	close_file_or_dir(fd, dirstream);