Remove use of and_call_original

As per NatService specific tests, remove need to have rSpec and_call_original
call in the test path - this is risky in an integration test.

This also aligns the method that we are using to test how many times the
edgeGateway has been updated, so is ripe for DRYing out.
Include LoadBalancer in general integration test

This is done by adding a new configuration that adds a load balancer
on top of the previous case of adding a nat and firewall in the same
config.
Fix overly long lines
Improve test names to reflect test content

We were previously checking for calls to Core::EdgeGateway for these
tests, but have now changed to counting the number of EdgeGateway
update tasks logged in the organization.

Fix the test names so that they reflect this change in test
behaviour.
Remove unnecessary test

This test is effectively a repetition of the test on line 83, so
is unnecessary.
Merge pull request #8 from alphagov/load_balancer_general_integration_test

[#64583056] Load balancer general integration test