SLING-3235 - additional readyness checks to cope with async config install at startup

git-svn-id: https://svn.apache.org/repos/asf/sling/trunk@1542223 13f79535-47bb-0310-9956-ffa450edef68
SLING-3147 - refresh Session before loading JCR resource bundle, needed for Oak

git-svn-id: https://svn.apache.org/repos/asf/sling/trunk@1542231 13f79535-47bb-0310-9956-ffa450edef68
Merge branch 'trunk' of http://git.apache.org/sling into sling-3223