Add missing close() of resources in both production code and tests

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