emailauth, passwordauth: Avoid leaving cgisess_* files in the system temp directory.

emailauth, passwordauth: Avoid leaving cgisess_* files in the system temp directory.

Due to the use/abuse of CGI::Session to generate a token for the login
process, a new session database was created for each login, and left behind
afterwards. While each file is small, with many logings this could bloat
the size of /tmp significantly. Fixed by making CGI::Session write to
/dev/null, since there does not seem to be a way to entirely prevent the
writing.

This commit was sponsored by Henrik Riomar on Patreon.