improved manager test coverage

internal/pkg/manager/manager_test.go

@@ -185,10 +185,10 @@ func TestManagerHBTiming(t *testing.T) {
 	hb := 100
 	pings := 10
 
-	// expected time with some tolerance for other events
-	expected := time.Duration(pings*hb+5) * time.Millisecond
+	// expected time with tolerance for other logic and worst case rand timeout
+	expected := time.Duration(pings*hb+15) * time.Millisecond
 
-	go manager.HeartBeat(ch, hb, 0, time.Millisecond)
+	go manager.HeartBeat(ch, hb, 1, time.Millisecond)
 
 	iter := 0
 	start := time.Now()