Enable $reply_self for group-reply, even with $metoo unset.

Enable $reply_self for group-reply, even with $metoo unset.

For a (r)eply, the $metoo variable does not have any effect because
there is a single recipient.

However with (g)roup reply, the To was initially set to the sender,
but subsequently removed my $nometoo.  The empty To line is then
replaced with the Cc line, resulting in a (logically correct but)
surprising outcome.

Change the behavior such that $nometoo will not strip a single To
recipient when $reply_self is set.