Fix test for Egress only policy

[MrTrustor]

One of our test case was using the following test FQDNNetworkpolicy:

apiVersion: networking.gke.io/v1alpha2
kind: FQDNNetworkPolicy
metadata:
  name: fqdnnetworkpolicy-valid
spec:
  podSelector: {}
  policyType: Egress
  egress:
    - to:
      - fqdns:
        - github.com
        - gitlab.com
      ports:
      - port: 443
        protocol: TCP

The section policyType: Egress is not valid and was ignored.
It should be:

policyTypes:
- Egress

I've fixed this mistake, and updated the unit test to make sure that we check the policyTypes on this example.

Fix #16