[SCTP]: Correctly handle AUTH parameters in unexpected INIT

When processing an unexpected INIT chunk, we do not need to
do any preservation of the old AUTH parameters.  In fact,
doing such preservations will nullify AUTH and allow connection
stealing.

Signed-off-by: Vlad Yasevich <vladislav.yasevich@hp.com>
Signed-off-by: David S. Miller <davem@davemloft.net>