server: no unrequested device-ready events (bnc#871135)

This bug caused e.g. bridges not going up from device-exists
even they already were in device-ready state before.
Merge pull request #253 from mtomaschewski/device-ready

server: no unrequested device-ready events (bnc#871135)
version 0.5.25
dhcp6: reset and allocate message buffer in build
Merge pull request #255 from mtomaschewski/dhcp6

dhcp6: reset and allocate message buffer in build