Say a module assigned and left out of its machine's composition as a condition (issue 380)

A push leaves out a module whose settings do not compose and sends the rest,
which is right, but only plan said so: nfs-server ran nowhere for days while
the operator believed it ran. The self-check now raises needs-operator for a
setting nobody gave, naming the setting and the command, and left-out for any
other cause; both warnings, cleared once the module composes or is unassigned.
status and node show list the same modules as assigned, not applied.

cmd/mesh-controller/build.go

@@ -835,6 +835,9 @@ type answers struct {
 	// public name on the machine went dark. The holds were correct; they were recorded only in the
 	// machine's own state file, and the one visible symptom was a count that did not add up.
 	untaken map[string]map[string]int
+	// leftOut is, per machine, every module of its set its composition leaves out, and why (novox/hq issue
+	// 380): assigned and not applied, which every push said only in passing. Not well while there is any.
+	leftOut map[string][]leftOutModule
 	// unheld is every module on a machine whose resources are applied through a seat nothing on
 	// that machine holds (novox/hq ADR 0207), with the modules that could hold it. Reported, not
 	// refused, until the switch — and while there is any, the mesh is not all well: the order the