This appears to have broken some 6rd. Revert "Ooops correct value here"

This reverts commit c93c2295780820e4d4deb8f11411d79120867648.
This appears to have broken some 6rd. Revert "Allow specifying a prefixlen for ipv4 address embedded. With it for normal operation is required to specify the other value of the ipv4 prefix. With it allow more than one stf instance to exist without bringing the others down"

This reverts commit ad398189f91fe4f5f40b70eb76e85f71dd77bbc5.