BPlusTree: CallLevel lock is never released in the case of exception

There is a possibility that CallLevel lock would never be released. 
And this is really happening if LockTimeout expires in NodeCache.

Here is the code in the constructor of RootLock:
   _locked = _exclusive ? _tree._selfLock.TryWrite(tree._options.LockTimeout) : _tree._selfLock.TryRead(tree._options.LockTimeout);
   Assert(_locked);
   Pin = _tree._storage.LockRoot(type);

If an exception is thrown in '_tree._storage.LockRoot(type)' then 
'_tree._selfLock' will never be released. 
So the code should be enclosed by try..catch:

try
{
    Pin = _tree._storage.LockRoot(type);
}
catch
{
    if (_exclusive)
       _tree._selfLock.ReleaseWrite();
    else
       _tree._selfLock.ReleaseRead();
    throw;
}

Original issue reported on code.google.com by Frame...@gmail.com on 28 May 2014 at 1:23

Jordy21 / csharptest-net

BPlusTree: CallLevel lock is never released in the case of exception #37