• Fix radix tree memory leakage when unloading modules using radix

trees. This happens because the logic inserting items into the radix
tree is allocating empty radix levels, when index zero does not
contain any items.

• Add proper error case handling, so that the radix tree does not end

up in a bad state, if memory cannot be allocated during insertion of
an item.

• Add check for inserting NULL items into the radix tree.
• Add check for radix tree getting too big.

MFC after: 1 week
Sponsored by: Mellanox Technologies