Add cleanup for test_show_auto_allocated_topology test

This patch makes sure that test_show_auto_allocated_topology
deletes resources that are created during its execution.

Before, the test didn't clean the following resources:
- network: auto_allocated_network
- subnets: auto_allocated_subnet_v4 & auto_allocated_subnet_v6
- router: auto_allocated_router

Story: 2007941
Task: 40406
Change-Id: I8cc77f7d47918d8329298ee32733d569294f11b7
1 file changed