There were framework.ExpectNoError(fmt.Errorf(..)) calls which just
raise an exception without actual value checks, they just raised the
specified error messages. These usages of framework.ExpectNoError()
seemed a little tricky, so this replaces them with corresponding check
functions for the readability.
Quite a few images are only used a few times in a few tests. Thus,
the images are being centralized into the agnhost image, reducing
the number of images that have to be pulled and used.
This PR replaces the usage of the following images with agnhost:
- fakegitserver
- hostexec
- liveness
- logs-generator
- no-snat-test
- no-snat-test-proxy
- port-forward-tester
