Add weak reference test for callback manager
Add weak reference test for callback manager

Adds a unit test to make sure the callback manager can
have weakly referenced functions as callbacks.

Change-Id: Ic811e8fe63bcde2d89cdb39f9a641cde1ebd9ddb

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