ContainerProxyTests Heisenbug

Seen failure in `ContainerProxyTest` at https://scans.gradle.com/s/4lb3ctstu5cqc/tests/xaqugzlgs2zxa-igyfqphtwknzs?openStackTraces=WzBd in _ContainerProxy should run an action after pausing the container_

```
java.util.NoSuchElementException: None.getClose stacktrace
at scala.None$.get(Option.scala:349)
at scala.None$.get(Option.scala:347)
at org.apache.openwhisk.core.containerpool.test.ContainerProxyTests.$anonfun$new$11(ContainerProxyTests.scala:379)
at akka.testkit.TestKitBase.poll$2(TestKit.scala:312)
at akka.testkit.TestKitBase.awaitAssert(TestKit.scala:329)
at akka.testkit.TestKitBase.awaitAssert$(TestKit.scala:301)
at akka.testkit.TestKit.awaitAssert(TestKit.scala:896)
at org.apache.openwhisk.core.containerpool.test.ContainerProxyTests.$anonfun$new$10(ContainerProxyTests.scala:366)
at akka.testkit.TestKitBase.within(TestKit.scala:360)
at akka.testkit.TestKitBase.within$(TestKit.scala:348)
at akka.testkit.TestKit.within(TestKit.scala:896)
at akka.testkit.TestKitBase.within(TestKit.scala:374)
at akka.testkit.TestKitBase.within$(TestKit.scala:374)
at akka.testkit.TestKit.within(TestKit.scala:896)
at org.apache.openwhisk.core.containerpool.test.ContainerProxyTests.$anonfun$new$9(ContainerProxyTests.scala:340)
at org.scalatest.OutcomeOf.outcomeOf(OutcomeOf.scala:85)
at org.scalatest.OutcomeOf.outcomeOf$(OutcomeOf.scala:83)
at org.scalatest.OutcomeOf$.outcomeOf(OutcomeOf.scala:104)
at org.scalatest.Transformer.apply(Transformer.scala:22)
at org.scalatest.Transformer.apply(Transformer.scala:20)
at org.scalatest.FlatSpecLike$$anon$1.apply(FlatSpecLike.scala:1682)
at org.scalatest.TestSuite.withFixture(TestSuite.scala:196)
at org.scalatest.TestSuite.withFixture$(TestSuite.scala:195)
at org.apache.openwhisk.core.containerpool.test.ContainerProxyTests.withFixture(ContainerProxyTests.scala:49)
at org.scalatest.FlatSpecLike.invokeWithFixture$1(FlatSpecLike.scala:1680)
at org.scalatest.FlatSpecLike.$anonfun$runTest$1(FlatSpecLike.scala:1692)
at org.scalatest.SuperEngine.runTestImpl(Engine.scala:289)

[2018-11-28T12:01:35.803Z] [INFO] [#tid_sid_testing] [ContainerProxy] [marker:invoker_collectLogs_start:194]
[2018-11-28T12:01:35.804Z] [INFO] [#tid_sid_testing] [ContainerProxy] [marker:invoker_collectLogs_finish:194:0]
[2018-11-28T12:01:35.808Z] [INFO] [#tid_sid_testing] [ContainerProxy] [marker:invoker_collectLogs_start:199]
[2018-11-28T12:01:35.809Z] [INFO] [#tid_sid_testing] [ContainerProxy] [marker:invoker_collectLogs_finish:199:0]
```