Copy v3-client API tests to the TO API tests Docker container now that the client directory is a symlink

[zrhoffman]

What does this PR (Pull Request) do?

#4968 made traffic_ops/client a symlink. Because the CiaB traffic_ops_integration_test Dockerfile copies in traffic_ops/client but not traffic_ops/client-v3, it fails to build the v3 API test.

This PR copies traffic_ops/client-v3 in the Dockerfile.

• This PR is not related to any Issue

Which Traffic Control components are affected by this PR?

• CDN in a Box
• Traffic Ops

What is the best way to verify this PR?

Run the API tests in CDN-in-a-Box, verify they pass:

docker-compose up --no-deps -d dns db smtp trafficops-perl trafficops
docker-compose -f docker-compose.traffic-ops-test.yml up --build integration

If this is a bug fix, what versions of Traffic Control are affected?

• master (e1eb046)

The following criteria are ALL met by this PR

• This PR fixes tests
• Intended behavior unchanged, documentation unnecessary
• An update to CHANGELOG.md is not necessary
• This PR includes any and all required license headers
• This PR does not include a database migration
• This PR DOES NOT FIX A SERIOUS SECURITY VULNERABILITY (see the Apache Software Foundation's security guidelines for details)

Additional Information