Fix unit tests under windows

Fix unit tests under windows

the following tests fail under windows because certain inputstreams
are not closed and files cannot be deleted because of that.  The
main problem I found is UnpackedObject.InflaterInputStream.close().
This method may throw exceptions found by checkValidEndOfStream()
but doesn't call super.close() before leaving. It is not clear to me
which resources a close() method should release before it throws an
exception. But those reseources which are not published to the
outside and which therefore cannot be closed by other means have to
be closed in all cases.
I changed the close() method to call super.close() under all
circumstances.

failing tests:
  testStandardFormat_LargeObject_TruncatedZLibStream(org.eclipse.jgit.storage.file.UnpackedObjectTest)
  testStandardFormat_LargeObject_TrailingGarbage(org.eclipse.jgit.storage.file.UnpackedObjectTest)
  testPackFormat_SmallObject(org.eclipse.jgit.storage.file.UnpackedObjectTest)

Change-Id: Id2e609a29e725aad953ff9bd88af6381df38399d
Signed-off-by: Christian Halstrick <christian.halstrick@sap.com>