Optimize query in _select_dhcp_ips_for_network_ids
Optimize query in _select_dhcp_ips_for_network_ids

Only query the DB for relevant columns instead of
all of the port columns.

Partial-Bug: #1373851
Change-Id: I32cd4a0bc6799ce77cea13188676308e3e641d19

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