Subnets should be set as lazy='join'
Subnets should be set as lazy='join'

Currently if one does a net-list tons of queries are issued against the
database as the default query mode is 'select' which performs a query when
the field is actually accessed. In this patch I change the the mode to
'joined' so subnets are loaded as the networks are loaded. Usually, there
are only 1 or 2 subnets on a network so loading this data shouldn't hurt.
This patch in my setup with 5000 networks reduces the net-list call from 27
seconds to 7! Woot Woot :)

Change-Id: I10eec4d79b522dfd685d3d2aa93a8d643104bba7
Closes-bug: 1298053

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