Action limits should be aborted when exceeding its memory limits test failure

Observed test failure in https://api.travis-ci.org/v3/job/541177267/log.txt

```
org.apache.openwhisk.core.limits.ActionLimitsTests > Action limits should be aborted when exceeding its memory limits STANDARD_OUT
Exception occurred during test execution: org.scalatest.exceptions.TestFailedException: error waiting for activation 31e261885fbb41bea261885fbb61bef4 for 60 seconds: Cannot find activation id from 'null'

org.apache.openwhisk.core.limits.ActionLimitsTests > Action limits should be aborted when exceeding its memory limits STANDARD_ERROR
org.scalatest.exceptions.TestFailedException: error waiting for activation 31e261885fbb41bea261885fbb61bef4 for 60 seconds: Cannot find activation id from 'null'
at org.scalatest.Assertions.newAssertionFailedException(Assertions.scala:528)
at org.scalatest.Assertions.newAssertionFailedException$(Assertions.scala:527)
at org.scalatest.FlatSpec.newAssertionFailedException(FlatSpec.scala:1685)
at org.scalatest.Assertions.fail(Assertions.scala:1089)
at org.scalatest.Assertions.fail$(Assertions.scala:1085)
at org.scalatest.FlatSpec.fail(FlatSpec.scala:1685)
at common.WskTestHelpers.withActivation(WskTestHelpers.scala:269)
at common.WskTestHelpers.withActivation$(WskTestHelpers.scala:260)
at org.apache.openwhisk.core.limits.ActionLimitsTests.withActivation(ActionLimitsTests.scala:56)
at common.WskTestHelpers.withActivation(WskTestHelpers.scala:253)
at common.WskTestHelpers.withActivation$(WskTestHelpers.scala:241)
at org.apache.openwhisk.core.limits.ActionLimitsTests.withActivation(ActionLimitsTests.scala:56)
at org.apache.openwhisk.core.limits.ActionLimitsTests.$anonfun$new$61(ActionLimitsTests.scala:464)
at org.apache.openwhisk.core.limits.ActionLimitsTests.$anonfun$new$61$adapted(ActionLimitsTests.scala:453)
at common.WskTestHelpers.withAssetCleaner(WskTestHelpers.scala:198)
at common.WskTestHelpers.withAssetCleaner$(WskTestHelpers.scala:193)
at org.apache.openwhisk.core.limits.ActionLimitsTests.withAssetCleaner(ActionLimitsTests.scala:56)
at org.apache.openwhisk.core.limits.ActionLimitsTests.$anonfun$new$60(ActionLimitsTests.scala:453)
```

Start by reproducing the failure in org.apache.openwhisk.core.limits.ActionLimitsTests, especially the test reported at ActionLimitsTests.scala:464, and inspect the activation wait path in common.WskTestHelpers.scala:269. Use the Travis log as the failure reference; done means the memory-limit action test completes with the expected aborted activation behavior instead of timing out with a null activation id.

Written by the indexing model from the issue text.