Make sure that failure to evaluate a tag against a single node does not make update-tag-rule's bg processing fail

When doing update-tag-rule, nodes get retagged using the updated tag in the background. If evaluating the updated tag against a single node failed, none of the nodes would get retagged properly. This change makes sure that other nodes get retagged, and that the evaluation failure is logged against the node(s) that caused the failure.

See https://tickets.puppetlabs.com/browse/RAZOR-249