[SCTP]: Fix local_addr deletions during list traversals.

Since the lists are circular, we need to explicitely tag
the address to be deleted since we might end up freeing
the list head instead.  This fixes some interesting SCTP
crashes.

Signed-off-by: Chidambar 'ilLogict' Zinnoury <illogict@online.fr>
Signed-off-by: Vlad Yasevich <vladislav.yasevich@hp.com>
Signed-off-by: David S. Miller <davem@davemloft.net>