SLING-3495 : using default timeout of 30s instead of 20s - plus using TimeoutProvider which allows to configure an additional factor - to adjust for slow machines, thanks @bdelacretaz for the pointer

git-svn-id: https://svn.apache.org/repos/asf/sling/trunk@1602899 13f79535-47bb-0310-9956-ffa450edef68