Improve unit test times
Improve unit test times

Revert the change using a temporary file for the database.
The sqlalchemy version is updated to >=0.7.8 (this includes
fixes for memory leaks).

Change-Id: Ib5d128edfef0f8e0afebaf408f7834fa3de2481a

openstack/networking-odl,openstack/neutron-vpnaas,gotostack/neutron-lbaas,gaolichuang/neutron-fwaas,FedericoRessi/networking-odl,gandelman-a/neutron-lbaas,openstack/neutron-vpnaas,schoksey/networking-odl,gaolichuang/neutron-fwaas,openstack/neutron-fwaas,gandelman-a/neutron-lbaas,dougwig/x-neutron-fwaas,openstack/neutron-fwaas,flavio-fernandes/networking-odl,openstack/networking-odl,citrix-openstack-build/neutron-lbaas,dougwig/x-neutron-vpnaas,gotostack/neutron-lbaas,citrix-openstack-build/neutron-vpnaas,citrix-openstack-build/neutron-fwaas,CiscoSystems/networking-odl,openstack/networking-odl,mestery/x-stackforge-odl,schoksey/networking-odl,FedericoRessi/networking-odl,flavio-fernandes/networking-odl,gandelman-a/neutron-lbaas,dougwig/x-neutron-lbaas,CiscoSystems/networking-odl,gotostack/neutron-lbaas