Bug 1808: Don't deserialize IPv4 payload in non-first fragments.

Protocol header, such as TCP header, is present only in the first fragment.
So the payload of IPv4 packet should be treated as raw bytes if the
fragmentation offset is not zero.

Change-Id: I508a8cfc3c074d5b18f638d80e68ee730e9b7034
Signed-off-by: Shigeru Yasuda <s-yasuda@da.jp.nec.com>
Merge "Bug 1808: Don't deserialize IPv4 payload in non-first fragments."