Fix radix lookup thread safety v3

Radix lookups would update the tree, leading to threading issues.

Ticket:
https://redmine.openinfosecfoundation.org/issues/1073

Changes since https://github.com/inliniac/suricata/pull/737
- fix scan-build warnings
- remove noisy debug statement

prscript:
- PR build: https://buildbot.suricata-ids.org/builders/inliniac/builds/112                                                                                                                                                                   
- PR pcaps: https://buildbot.suricata-ids.org/builders/inliniac-pcap/builds/33