aga,agar: Non-equal edge costs for parallel test graph

aga,agar: Non-equal edge costs for parallel test graph

At the moment the "parallel" test graph just uses the default cost of 1
for all the links between the two nodes.  This patch changes that so that
the links have cost 2, except (optionally) one with cost 1.  This provides
a useful test for the Dijkstra's algorithm implementation to ensure that
it picks the correct link for the shortest path.

Signed-off-by: David Gibson <david@gibson.dropbear.id.au>