0d7cd66652 broke validation for hashes with options
such as those generated with `mkpasswd --method=sha-512 --rounds=1000000`:
$6$rounds=1000000$xpzZ6Rfg873gZnDY$RxS7lpVnohfDrrKG3lt9UFHED1KoiPGzH7zQv/HzwalZepo/IfFtxw05ap25duEJSKYhC14.Fn9eXszEpWVtF.
This fixes it.