policy: add extra debug to ifcondition functions

NI_LOG_DEBUG2 lvelel needed to enable it.
ifcondition: Fix <child> handling

Handle <child> the same way as <and>.
Merge pull request #329 from pwieczorkiewicz/child_policy

nanny: make policy application mechanism aware of children dependency
Merge pull request #330 from mtomaschewski/state-drop

lib: fixed to drop state before deleting netdev
Merge branch 'master' into testing