Rally: decrease SLA for avg list of ports and nets
Rally: decrease SLA for avg list of ports and nets

In a normal gate run these are returning in 2 seconds each
on average. Let's reduce the SLA of these from 15 to 5 now
to help prevent future performance regressions in this area.

Change-Id: Iae174c95d214c83d6726a3d3bd339dde7886af4f

mahak/neutron,eayunstack/neutron,mahak/neutron,noironetworks/neutron,openstack/neutron,eayunstack/neutron,openstack/neutron,openstack/neutron,huntxu/neutron,mahak/neutron,huntxu/neutron,noironetworks/neutron