libfdisk: (dos) be more robust about max number of partitions

libfdisk: (dos) be more robust about max number of partitions

It seems the previous MAXIMUM_PARTS bug fix has not been generic
enough. Let's use the check for all dos_add_partition().

This patch also remove libfdisk attempt to be smart and search for
unused primary partition. If you need more than 60 partition in MBR
than you have a different problem that cannot be solved by libfdisk
...

References: http://github.com/karelzak/util-linux/commit/b80fb30a5b79ce2cc8c7486e1435ec061aa79e2f
Addresses: https://github.com/karelzak/util-linux/issues/1022
Signed-off-by: Karel Zak <kzak@redhat.com>