The helper method MemorySessionImpl::addOrCleanupIfFail should try to add a close action to the session and, if an exception occur, should call the cleanup action and propagate the exception outwards.

The implementation currently does not propagate the exception. While this doesn't affect correctness (worst thing that can happen is that a client might obtain a memory segment which, upon subsequent access, seems closed), it would be better to fix, so that errors are reported as soon as possible to clients.