domain-control: switched to resolver-aware trigger-driven notification logic.

domain-control: switched to resolver-aware trigger-driven notification logic.

Switched client notification logic from table stamp-based to
trigger-driven. Also block client updates if/while ruleset-
resolution is active. Schedule an extra update when resolution
is finished.

Resolver-activity is tracked by subscribing to start/done/fail
events emitted by the resolver and calculating started but un-
finished events.