GlobalCursorIdCache::visitAllCursorManagers should not uassert on encountering a view

When iterating over collection CursorManager instances we will:

1. Build a list of namespaces from the CursorManager::_idToNss map under the CursorManager::_mutex.
2. Release the CursorManager::_mutex and then iterate over the namespaces.
3. MODE_IS lock each namespace using AutoGetCollection
4. Under the lock, perform an operation on the collection's CursorManager.

It is possible that in between releasing CursorManager::_mutex and locking the collection namespace that a collection is dropped and recreated as a view. If this occurs, the call to AutoGetCollection will uassert when encountering the view. Instead we should change our collection locking mechanism to recognize that a namespace is now a view and skip the namespace, rather than uassert.