Stop the controller's tests waiting out fixed intervals

Reading the build events waited two seconds on every queue read, the race
detector's exit sleep cost a second per command line a test runs, and the
lease and plan-wait tests waited out production intervals (novox/hq issue 591).

cmd/mesh-controller/plans_follow.go

@@ -30,8 +30,9 @@ var maxPlanWait = link.LongestAnswer - planWaitStart
 // answered that the call is still running, and `calls` with its id says what came of it.
 const planWaitStart = 5 * time.Second
 
-// planWaitEvery is how often a wait reads the plan again.
-const planWaitEvery = time.Second
+// planWaitEvery is how often a wait reads the plan again. A variable so a test reads it more often
+// (novox/hq issue 591).
+var planWaitEvery = time.Second
 
 // The things a wait waits until.
 var planWaitUntil = []string{"moved", "tier", "done"}