Fix https://issues.apache.org/bugzilla/show_bug.cgi?id=57016
When using the PersistentValve do not remove sessions from the store when persisting them.

git-svn-id: https://svn.apache.org/repos/asf/tomcat/tc7.0.x/trunk@1627630 13f79535-47bb-0310-9956-ffa450edef68