Add more tests for EVCs with static paths + dynamic_backup_path

[viniarck]

We have very little e2e test cov for these use cases:

• Static EVC with just primary_path + dynamic_backup_path
• Static EVC with both primary_path and backup_path + dynamic_backup_path

https://github.com/kytos-ng/kytos-end-to-end-tests/blob/master/tests/test_e2e_11_mef_eline.py#L120

These should work, but they haven't been tested/explored that extensively, especially the convergence part needs to be more stressed out to ensure it's always behaving as expected.

@RenataFrez has found a case in prod where it didn't find a path during convergence, so let's use this issue here as a starting point to map the cases/scenarios that AmLight network engineers are using in prod, and which ones we should cover better. We'll continue from here and eventually stress test it more too.