fix policy routing (PBR) test for known priority
The step "Create PBR files for profile..." wrote rules without specifying
a priorty. When omitting the priority with ip rule add, kernel automatically
chooses a priority (one less than the lowest existing priority).
The test breaks if there are unexpected rules there. That can be the case when the VRF module is loaded (which adds a rule "1000:from all lookup [l3mdev-table]").
Avoid that by explicitly selecting the rule priority.
While at it, reduce the sleep(3) to sleep(1). That really should suffice, especially because the behave step only writes a file. It's unclear why we sleep there at all.