Fixes/improvements containing the following six listed changes

1.Fix for vpninterfaces using portuuid as string as vpnInfName
2. displayFib Karaf CLI added
3. Change to proceed with nexthop null too in case of absence of any
tunnel
4. Calling removeGroup API instead of syncRemoveGroup to align with OVS
5. Additional check in getL3VPN
6. Retriving first fixed IP for port without looping over as per the
current support for single fixed IP per neutron port

Change-Id: Id13cfb1c84f57a039ca025076155745853cb0e7c
Signed-off-by: Abhinav Gupta <abhinav.gupta@ericsson.com>