XBEAN-270 no real way to auto destroy the scanner thread so adding a manual method

git-svn-id: https://svn.apache.org/repos/asf/geronimo/xbean/trunk@1613224 13f79535-47bb-0310-9956-ffa450edef68
ensuring to flush tasks before destruction

git-svn-id: https://svn.apache.org/repos/asf/geronimo/xbean/trunk@1613225 13f79535-47bb-0310-9956-ffa450edef68