Do not save container log by default. (#1339)

Run stem cell container on a scheduled Future (but after killStragglers has finished).
Include toBeRemoved in slack calculation.
diff --git a/tests/src/whisk/core/container/test/ContainerPoolTests.scala b/tests/src/whisk/core/container/test/ContainerPoolTests.scala
index 9a2a50d..4ffa786 100644
--- a/tests/src/whisk/core/container/test/ContainerPoolTests.scala
+++ b/tests/src/whisk/core/container/test/ContainerPoolTests.scala
@@ -68,7 +68,7 @@
             ++ WhiskAuthStore.requiredProperties)
     assert(config.isValid)
 
-    val pool = new ContainerPool(config, 0, InfoLevel, true)
+    val pool = new ContainerPool(config, 0, InfoLevel, true, true)
     pool.logDir = "/tmp"
 
     val datastore = WhiskEntityStore.datastore(config)