Make sure test repositories are closed

Make sure test repositories are closed

Some repositories created during tests are not added to the 'toClose'
list in LocalDiskRepositoryTestCase. Therefore when the tests end
we may have open FileHandles and on Windows this may cause the
tests to fail because we can't delete those files.

This is fixed by adding the possibility to explicitly add
repositories to the list of repos which are closed automatically.

Change-Id: I1261baeef4c7d9aaedd7c34b546393bfa005bbcc
Signed-off-by: Christian Halstrick <christian.halstrick@sap.com>