fix test nit
fix test nit

although 2G of ram is rare, but test should not
break if vm got that small ram.

Change-Id: Ic3efbe0767abca9c7ac25b58a7fb2af97e210d45

mahak/neutron,openstack/neutron,mahak/neutron,openstack/neutron,openstack/neutron,mahak/neutron