saslserv/main: accept grouped nicknames

Due to popular request, finish what was started by ff19f558a24d.
Can't say I like this, but it was easy to do, and I guess I should
continue with the "usability" line anyway.
saslserv/main: _actually_ accept grouped nicknames

I forgot to actually test with NICK/USER/CAP END, so never noticed the
"account ?? dropped" error. Sigh.