There are some situations where it is valid to use
INGRESS_TRAFFIC_ALL in conjunction with the load balancer.
Currently it is not possible to override the
INGRESS_TRAFFIC_INTERNAL_LOAD_BALANCER ingress setting to
achieve this if var.enable_load_balancer == true.

This commit implements a matrix test job to run multiple
Terraform integration tests in parallel. It also implements
a cleanup script to ensure that failed test runs do not leave
infrastructure deployed which would cost money!