[Radix] Have the radix tree cleanup after itself
Summary: So far, the tree would leak its internals instead of freeing them properly. This patch ensures that the tree will cleanup after itself properly.
../configure --with-sanitizers=address make src/test/test_bitcoin ./src/test/test_bitcoin -t radix_tests
Checks that there are no more leaks.
Reviewers: #bitcoin_abc, jasonbcox
Reviewed By: #bitcoin_abc, jasonbcox
Subscribers: jasonbcox, teamcity, schancel
Differential Revision: https://reviews.bitcoinabc.org/D2385