Add unit test for add_vxlan in test_linux_ip_lib
Add unit test for add_vxlan in test_linux_ip_lib

This patch adds unit tests for the add_vxlan function in the test_linux_ip_lib.py
file.

Fixes bug: 1291974

Change-Id: I0238bedab7a3566aff1115a091ada494a01d2e02

jacknjzhou/neutron,asgard-lab/neutron,cisco-openstack/neutron,yamahata/tacker,vveerava/Openstack,klmitch/neutron,leeseulstack/openstack,alexandrucoman/vbox-neutron-agent,blueboxgroup/neutron,sasukeh/neutron,Metaswitch/calico-neutron,gkotton/neutron,barnsnake351/neutron,infobloxopen/neutron,igor-toga/local-snat,sasukeh/neutron,silenci/neutron,eayunstack/neutron,swdream/neutron,yamahata/tacker,silenci/neutron,bgxavier/neutron,vveerava/Openstack,projectcalico/calico-neutron,mattt416/neutron,noironetworks/neutron,vveerava/Openstack,CiscoSystems/neutron,paninetworks/neutron,gopal1cloud/neutron,takeshineshiro/neutron,blueboxgroup/neutron,leeseulstack/openstack,jacknjzhou/neutron,swdream/neutron,leeseulstack/openstack,Metaswitch/calico-neutron,miyakz1192/neutron,mandeepdhami/neutron,yamahata/tacker,Stavitsky/neutron,bgxavier/neutron,vbannai/neutron,SamYaple/neutron,yuewko/neutron,vivekanand1101/neutron,rdo-management/neutron,leeseuljeong/leeseulstack_neutron,NeCTAR-RC/neutron,JianyuWang/neutron,adelina-t/neutron,adelina-t/neutron,openstack/neutron,mattt416/neutron,asgard-lab/neutron,apporc/neutron,waltBB/neutron_read,SmartInfrastructures/neutron,dhanunjaya/neutron,vbannai/neutron,pnavarro/neutron,noironetworks/neutron,cloudbase/neutron-virtualbox,aristanetworks/neutron,yanheven/neutron,takeshineshiro/neutron,virtualopensystems/neutron,wolverineav/neutron,yuewko/neutron,jumpojoy/neutron,MaximNevrov/neutron,Stavitsky/neutron,cisco-openstack/neutron,sebrandon1/neutron,alexandrucoman/vbox-neutron-agent,vivekanand1101/neutron,CiscoSystems/neutron,mahak/neutron,gkotton/neutron,eonpatapon/neutron,glove747/liberty-neutron,klmitch/neutron,mahak/neutron,cloudbase/neutron,igor-toga/local-snat,jerryz1982/neutron,javaos74/neutron,suneeth51/neutron,eonpatapon/neutron,watonyweng/neutron,waltBB/neutron_read,barnsnake351/neutron,cloudbase/neutron,virtualopensystems/neutron,antonioUnina/neutron,antonioUnina/neutron,redhat-openstack/neutron,glove747/liberty-neutron,magic0704/neutron,dims/neutron,NeCTAR-RC/neutron,paninetworks/neutron,CiscoSystems/neutron,leeseuljeong/leeseulstack_neutron,mmnelemane/neutron,rdo-management/neutron,JioCloud/neutron,bigswitch/neutron,mmnelemane/neutron,watonyweng/neutron,cernops/neutron,SamYaple/neutron,SmartInfrastructures/neutron,gopal1cloud/neutron,huntxu/neutron,JianyuWang/neutron,infobloxopen/neutron,dims/neutron,leeseuljeong/leeseulstack_neutron,shahbazn/neutron,chitr/neutron,projectcalico/calico-neutron,jumpojoy/neutron,cloudbase/neutron-virtualbox,cernops/neutron,huntxu/neutron,openstack/neutron,yanheven/neutron,blueboxgroup/neutron,javaos74/neutron,suneeth51/neutron,virtualopensystems/neutron,apporc/neutron,wenhuizhang/neutron,magic0704/neutron,jerryz1982/neutron,aristanetworks/neutron,wenhuizhang/neutron,bigswitch/neutron,miyakz1192/neutron,eayunstack/neutron,dhanunjaya/neutron,skyddv/neutron,vbannai/neutron,gkotton/neutron,wolverineav/neutron,MaximNevrov/neutron,sebrandon1/neutron,mahak/neutron,chitr/neutron,openstack/neutron,redhat-openstack/neutron,neoareslinux/neutron,mandeepdhami/neutron,shahbazn/neutron,skyddv/neutron,JioCloud/neutron,neoareslinux/neutron,pnavarro/neutron