send-email: --no-signed-off-cc should suppress 'sob' cc

send-email: --no-signed-off-cc should suppress 'sob' cc

The logic to countermand suppression of Cc to the signers with a more
explicit --signed-off-by option done in 6564828 (git-send-email:
Generalize auto-cc recipient mechanism) suffers from a double-negation
error.

A --signed-off-cc option, when false, should actively suppress CC: to be
generated out of S-o-b lines, and it should refrain from suppressing when
it is true.

It also fixes "(sob) Adding cc:" status output; earlier it included the
line terminator LF inside '%s', which was totally bogus.

Signed-off-by: Junio C Hamano <gitster@pobox.com>