close OPC package before assertion, otherwise the test fails on Win7 (unix-based systems always pass)

git-svn-id: https://svn.apache.org/repos/asf/poi/trunk@982911 13f79535-47bb-0310-9956-ffa450edef68

src/ooxml/testcases/org/apache/poi/openxml4j/opc/TestPackage.java

@@ -471,6 +471,7 @@ public final class TestPackage extends TestCase {
             fail("You shouldn't be able to call save(File) to overwrite the current file");
         } catch(InvalidOperationException e) {}
 
+        p.close();
         // Delete it
         assertTrue(tempFile.delete());