Make plugin deallocation check optional
Make plugin deallocation check optional

The fix for memory leakage in the related bug added a check for plugin
deallocation that performed a call to gc.collect() after every test.
This had the side-effect of increasing test execution time by ~50%, so
this patch makes the check optional via an environment variable
(OS_CHECK_PLUGIN_DEALLOCATION).

It may make sense to create a periodic job that runs with the check
enabled, but otherwise the check can be used by developers for
debugging purposes.

Change-Id: I9ebe663abbc4e4ff3a62d807d5a3230c2ecccd07
Related-Bug: #1234857

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