SLING-3214 - some utility methods have moved to the new HttpTest class

git-svn-id: https://svn.apache.org/repos/asf/sling/trunk@1536693 13f79535-47bb-0310-9956-ffa450edef68
SLING-3215 - switch to JUnit4-style tests, to be able to use RetryRule later

git-svn-id: https://svn.apache.org/repos/asf/sling/trunk@1536694 13f79535-47bb-0310-9956-ffa450edef68