tests: e2e test for POST v1/evc/expected_flows and POST v1/evc/check_consistency

[viniarck]

It'd be great to have two test cases covering the following:

1. POST v1/evc/expected_flows confirming at least one inter EVC

2. Cover the fix action on POST v1/evc/check_consistency

• Use an existing topo, confirm the flows are as expected (similarly to the prior test case)
• With flow_manager force deletion of a set of existing flows of an EVC (this will result in missing flows when check_consistency is called)
• With flow_manager force adding alien flows with the same cookeis (this will result in alien flows when ``check_consistency` is called)
• Call POST v1/evc/check_consistency with inconsistency_acion=fix