https://issues.apache.org/jira/browse/AMQ-5266 tidy up leveldb impl with additional scenario tests
https://issues.apache.org/jira/browse/AMQ-5266 track cursor pending additions size in debug logging
https://issues.apache.org/jira/browse/AMQ-5407

Allow config of enabled protocols for nio+ssl and stomp+nio+ssl etc to
match the capability of the non-nio transports.