add tests for the httplog package

Currently there are no tests for the httplog package. This patch adds
an initial set of tests and improves test coverage.
Merge pull request #541 from kelseyhightower/httplog_test

add tests for the httplog package
Remove unnecessary expectNoError helper function

This patch completes a TODO item for the kubecfg package test suite by
removing the expectNoError helper function, which does not reduce enough
typing to justify its usage.
Add test cases for Docker image name parsing and cleanup

The tests for Docker image name parsing are repetitive and do not
cover enough test cases.

Refactor the tests to use table testing and add additional test cases.
Merge pull request #546 from kelseyhightower/kubecfg_tests

Remove unnecessary expectNoError helper function
Merge pull request #547 from kelseyhightower/kubelet_tests

Add test cases for Docker image name parsing and cleanup
Improve test coverage for the health package and remove mocks

The current tests for the health package utilize a fake HTTP client
for testing health checks and only cover a limited set of test cases.

This patch removes the need for mocks by using the httptest package
from the standard library. After removing the fake HTTP client a bug
was found in the health.Check function; it incorrectly assumes that
a http.Response is always non-nil. Fix the issue by moving the defer
that closes the http.Response.Body after error handling.

Related tests in the registry package have be refactored to work with
the changes made to the health.Check function. All methods that implement
the health.HTTPGetInterface interface now return a http.Response with
with a noop http.Response.Body.

This patch does not introduce any changes in behavior.