A new assignment whose trunk build was not done fell through the rules
with nothing said: no want, no neither-list entry, no log line, and the
rule holding it back was computed and dropped. The pass now logs the rule
when a node's reason appears or changes and when it has a want again, one
line per change. A node whose want is removed and that does not run the
module gets the reason in that removed want's words, so assigner_want
answers why; a node with no key gets no removed want, since its node agent
would then remove the module and stop holding its resources back.
jschoubben
d4a054bfed