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

This reverts commit f44606d1678d2a7411b7b27c20fa166214a8ce02.
fsm: wait for existing configration workers (bnc#876855, bnc#880515)

When interface shows up late (but the configuration is present)
we wait for it until WAIT_FOR_INTERFACES timeout.
Merge pull request #302 from pwieczorkiewicz/late_ifaces

Handling of late interfaces (bnc#876855, bnc#880515)