Remove NO_SENDMAIL and all it masks, except one

Remove NO_SENDMAIL and all it masks, except one

The next step in the removal of Sendmail is to remove all the components
that NO_SENDMAIL masked, and then remove the internal NO_SENDMAIL knob
itself.

There is one component that got unmasked though: the etc/sendmail
dragonfl*.mc files.  I think we may need to keep building these, and
they require contrib/sendmail-8.14 source files.  I'll figure out what
needs to have to remove the contrib directory later.