Revert "XXX: adduser with extrausers database"
Revert "XXX: adduser with extrausers database"

This is more meant for console-conf on snappy; doesn't quite apply
to standard subiquity.

This reverts commit 4695735d795715e61db0ef86b871f7dc18c72f37.

CanonicalLtd/subiquity,CanonicalLtd/subiquity