In plan summary, be more honest about force-new changes.

Previously the plan summary output would consider -/+ diffs as changes
even though they actually destroy and create instances. This was
misleadning and inconsistent with the accounting that gets done for the
similar summary written out after "apply".

Instead we now count the -/+ diffs as both adds and removes, which should
mean that the counts output in the plan summary should match those in
the apply summary, as long as no errors occur during apply.

This fixes #3163.

command/plan.go

@@ -136,9 +136,9 @@ func (c *PlanCommand) Run(args []string) int {
 	c.Ui.Output(c.Colorize().Color(fmt.Sprintf(
 		"[reset][bold]Plan:[reset] "+
 			"%d to add, %d to change, %d to destroy.",
-		countHook.ToAdd,
-		(countHook.ToChange + countHook.ToRemoveAndAdd),
-		countHook.ToRemove)))
+		countHook.ToAdd+countHook.ToRemoveAndAdd,
+		countHook.ToChange,
+		countHook.ToRemove+countHook.ToRemoveAndAdd)))
 
 	if detailed {
 		return 2