Decreased the log level on a message relating to "purging" the cache.
In this case, no data is lost, its just a normal cleanup job.

Review at http://gwt-code-reviews.appspot.com/1447823

Review by: fabbott@google.com

git-svn-id: https://google-web-toolkit.googlecode.com/svn/trunk@10326 8db76d5a-ed1c-0410-87a9-c151d255dfc7