Comment 7 for bug 1898129

Tested this patch with netinstall by legacy installer(aka debian-installer).
Works well!
Just added into preseed:

d-i preseed/early_command string \
wget -q http://myhost.com/files/packages/partman-crypto_101ubuntu4+luksopts1_amd64.udeb ; \
udpkg -i partman-crypto_101ubuntu4\+luksopts1_amd64.udeb
d-i partman-crypto/luksformat_options string --type luks1