tests: Ensure that the scale_up.py script tests for actual sharp installed routes...

tests: Ensure that the scale_up.py script tests for actual sharp installed routes first

The scale_up.py script used by several tests installs 50k routes into the rib from
sharpd.  It is first looking for the results in the bgp database.  Let's ensure
that the routes are actually installed into the rib first before looking in
the bgp tables.  This should help situations where the system is under extreme
load.

Signed-off-by: Donald Sharp <sharpd@nvidia.com>