BUG 1341529

- if the packet from a resident VM has to go out on physical interface
and if vrouter needs to fragment the packet post tunnel header updation,
fragment only if DF bit is net set. Else, trap the packet to agent for
ICMP error reports

Change-Id: I1d7af762d1b3e095701e24f78737c31bcb9989cc
Merge "BUG 1341529"