Fix external name configuration for ECS Service

[turkenh]

Description of your changes

This PR fixes ECS Service external name configuration and adds a working/tested example.

Fixes #170

I have:

• [x] Read and followed Crossplane's contribution process.
• [x] Run make reviewable to ensure this PR is ready for review.

How has this code been tested

Using the (renamed) example manifest which is also added in this PR.

kubectl get -f examples/ecs/service.yaml -w
NAME                      READY   SYNCED   EXTERNAL-NAME             AGE
sample-service-by-hasan                    sample-service-by-hasan   2s
sample-service-by-hasan                    sample-service-by-hasan   35s
sample-service-by-hasan                    sample-service-by-hasan   35s
sample-service-by-hasan                    sample-service-by-hasan   35s
sample-service-by-hasan   False   True     sample-service-by-hasan   35s
sample-service-by-hasan   False   True     sample-service-by-hasan   35s
sample-service-by-hasan   False   True     sample-service-by-hasan   59s
sample-service-by-hasan   False   True     sample-service-by-hasan   63s
sample-service-by-hasan   False   True     sample-service-by-hasan   63s
sample-service-by-hasan   True    True     sample-service-by-hasan   77s
sample-service-by-hasan   True    True     sample-service-by-hasan   111s

[github-actions[bot]]

Successfully created backport PR #175 for release-0.4.