Cockpit: cockpit-storaged: tang keyserver address from an untrusted luks header clevis token reaches curl's argument vector as an option

A flaw was found in cockpit-storaged. A Tang keyserver address read from a clevis token in a LUKS header is concatenated into curl's argument vector without a "--" separator. An address beginning with "-" is parsed by curl as an option instead of a hostname, allowing an attacker who can attach a crafted LUKS/clevis block device (for example, a local unprivileged user with an active console or desktop login session) to have an administratively-privileged Cockpit user unknowingly trigger curl option injection when editing the device's Tang keyserver settings. This can lead to arbitrary file read or write as the Cockpit session user.