ipv6: added address,prefix,nduseropt event tracers

Moved debug dumps from event processing code to explicit
trace functions usable as event callback handlers.
wickedd: enabled address,prefix,nduseropt events
dhcp6: try to start on device-change event in auto mode
address: expose flags via dbus and show in ifstatus
Merge pull request #399 from mtomaschewski/bnc889981

address: enable events and expose flags (partial bnc#889981)
Remove config checks from ni_dhcp4_fsm_commit_lease

Signed-off-by: Olaf Hering <olaf@aepfle.de>
Make ni_dhcp4_fsm_commit_lease static

Signed-off-by: Olaf Hering <olaf@aepfle.de>