sctp: enable cookie-echo retransmission transport switch

This patch enables cookie-echo retransmission transport switch
feature. If COOKIE-ECHO retransmission happens, it will be sent
to the address other than the one last sent to.

Signed-off-by: Gui Jianfeng <guijianfeng@cn.fujitsu.com>
Signed-off-by: Vlad Yasevich <vladislav.yasevich@hp.com>