spamassassin: workaround for issue #444

and...
    use tests from spamd output (if sent)
    set the contents of a header to '' if undefined
spamassassin: restored empty string test (vs false)
spamassassin: remove hack, insert fix

I think.  So far, so good.
spamassassin: comment out a couple log entries
Merge pull request #445 from msimerson/spamassassin

Merged