Bug 8864: DNAT to SNAT traffic is getting failed on same DPN for VXLAN

Bug 8864: DNAT to SNAT traffic is getting failed on same DPN for VXLAN

Problem Description:
=========================
DNAT to SNAT traffic is getting failed on same hypervisor for External
VXLAN Provider Type

Solution:
===========
Have added the follwing flow install/remove code to handle this problem
for external VXLAN provider type (EVPN_RT5)

Install the flow L3_FIB_TABLE (table=21)-> INBOUND_NAPT_TABLE (table=44)
(FIP VM on DPN1 is responding back to external fixed Ip on DPN1 itself.
ie. same Hypervisor){DNAT to SNAT Intra DC traffic}

Change-Id: Id6670876a42ab0a7e89abee705bb0848a642e8df
Signed-off-by: karthikeyan <karthikeyan.k@altencalsoftlabs.com>