SCTP: Discard OOTB packetes with bundled INIT early.

RFC 4460 and future RFC 4960 (2960-bis) specify that packets
with bundled INIT chunks need to be dropped.  We currenlty do
that only after processing any leading chunks.  For OOTB chunks,
since we already walk the entire packet, we should discard packets
with bundled INITs.

There are other chunks chunks that MUST NOT be bundled, but the spec
is silent on theire treatment.  Thus, we'll leave their teatment
alone for the moment.

Signed-off-by: Vlad Yasevich <vladislav.yasevich@hp.com>
Acked-by: Wei Yongjun <yjwei@cn.fujitsu.com>