Ensure mocks for lla allocator _write in test_agent
Ensure mocks for lla allocator _write in test_agent

The test test_create_dvr_fip_interfaces_for_restart_l3agent_case was
causing a file fip-linklocal-networks to be created when the tests are
run, this patch ensures that the correct part of the LinkLocalAllocator
is patched to prevent this in the test case.

Change-Id: Ifd0cae56324364b281a9279047b26a182b77905a
Closes-Bug: 1450090

NeCTAR-RC/neutron,vivekanand1101/neutron,dims/neutron,JianyuWang/neutron,mandeepdhami/neutron,takeshineshiro/neutron,barnsnake351/neutron,glove747/liberty-neutron,dims/neutron,sebrandon1/neutron,bigswitch/neutron,bigswitch/neutron,watonyweng/neutron,miyakz1192/neutron,SmartInfrastructures/neutron,glove747/liberty-neutron,silenci/neutron,skyddv/neutron,barnsnake351/neutron,shahbazn/neutron,vivekanand1101/neutron,miyakz1192/neutron,cloudbase/neutron,mattt416/neutron,eayunstack/neutron,jacknjzhou/neutron,mmnelemane/neutron,huntxu/neutron,jumpojoy/neutron,chitr/neutron,mahak/neutron,wolverineav/neutron,jumpojoy/neutron,suneeth51/neutron,wenhuizhang/neutron,adelina-t/neutron,eayunstack/neutron,jerryz1982/neutron,antonioUnina/neutron,igor-toga/local-snat,mandeepdhami/neutron,sasukeh/neutron,asgard-lab/neutron,takeshineshiro/neutron,noironetworks/neutron,openstack/neutron,igor-toga/local-snat,chitr/neutron,javaos74/neutron,SamYaple/neutron,openstack/neutron,huntxu/neutron,swdream/neutron,JianyuWang/neutron,yuewko/neutron,antonioUnina/neutron,MaximNevrov/neutron,bgxavier/neutron,infobloxopen/neutron,yuewko/neutron,sasukeh/neutron,neoareslinux/neutron,shahbazn/neutron,eonpatapon/neutron,klmitch/neutron,dhanunjaya/neutron,cloudbase/neutron,paninetworks/neutron,jerryz1982/neutron,eonpatapon/neutron,openstack/neutron,cisco-openstack/neutron,javaos74/neutron,sebrandon1/neutron,noironetworks/neutron,SamYaple/neutron,dhanunjaya/neutron,JioCloud/neutron,SmartInfrastructures/neutron,cisco-openstack/neutron,asgard-lab/neutron,mmnelemane/neutron,JioCloud/neutron,wenhuizhang/neutron,infobloxopen/neutron,mahak/neutron,jacknjzhou/neutron,NeCTAR-RC/neutron,yanheven/neutron,mahak/neutron,neoareslinux/neutron,swdream/neutron,suneeth51/neutron,mattt416/neutron,silenci/neutron,MaximNevrov/neutron,watonyweng/neutron,wolverineav/neutron,adelina-t/neutron,yanheven/neutron,bgxavier/neutron,apporc/neutron,paninetworks/neutron,skyddv/neutron,apporc/neutron,klmitch/neutron