Add missing close() of resources in both production code and tests
Use revert() instead of close() on OCPPackage in some places to not re-write the file unnecessarily.
This should now run tests without leftover file handles when checked with file leak detector and
allows to find newly introduced cases more easily.

git-svn-id: https://svn.apache.org/repos/asf/poi/trunk@1648160 13f79535-47bb-0310-9956-ffa450edef68