smtp: Fixed sending of double CRLF caused by first in EOB

If the mail sent during the transfer contains a terminating <CRLF> then
we should not send the first <CRLF> of the EOB as specified in RFC-5321.

Additionally don't send the <CRLF> if there is "no mail data" as the
DATA command already includes it.

tests/data/test905

@@ -52,7 +52,6 @@ QUIT
 </protocol>
 <upload>
 mail body
-
 .
 </upload>
 </verify>