cisco: Do not change supported_extension_aliases directly
cisco: Do not change supported_extension_aliases directly

cisco network plugin extends supported_extension_aliases in __init__
but supported_exntension_aliases is a class attribute and it is not
reset to the original even after each unit test finished.
To avoid this this patch copies supported_extension_aliases to
an instance attribute and extends it to ensure the class variable
is not changed. This reduces unnecessary logs in unit tests.

Change-Id: I3a7313f5ca2d10b1ae6ea961d9d05611aee055c0
Closes-Bug: #1292742

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