discovery+routing: cancel dependent jobs if parent validation fails

Previously, we would always allow dependent jobs to be processed,
regardless of the result of its parent job's validation. This isn't
correct, as a parent job contains actions necessary to successfully
process a dependent job. A prime example of this can be found within the
AuthenticatedGossiper, where an incoming channel announcement and update
are both processed, but if the channel announcement job fails to
complete, then the gossiper is unable to properly validate the update.
This commit aims to address this by preventing the dependent jobs to
run.

routing/router.go

@@ -967,7 +967,8 @@ func (r *ChannelRouter) networkHandler() {
 					update.msg,
 				)
 				if err != nil {
-					if err != ErrVBarrierShuttingDown {
+					if err != ErrVBarrierShuttingDown &&
+						err != ErrParentValidationFailed {
 						log.Warnf("unexpected error "+
 							"during validation "+
 							"barrier shutdown: %v",
@@ -985,7 +986,11 @@ func (r *ChannelRouter) networkHandler() {
 
 				// If this message had any dependencies, then
 				// we can now signal them to continue.
-				validationBarrier.SignalDependants(update.msg)
+				allowDependents := err == nil ||
+					IsError(err, ErrIgnored, ErrOutdated)
+				validationBarrier.SignalDependants(
+					update.msg, allowDependents,
+				)
 				if err != nil {
 					return
 				}