Investigate random tests failures

[zpbappi]

Tests don't fail in local development machines, even when they are running in parallel. However, often they fail in AppVeyor. My guess- Thread related issues. We don't have enough data to conclude. The failures are not even reproducible. Here are two such recent failures:

1. https://ci.appveyor.com/project/VlingoNetOwner/vlingo-net-actors/builds/21000676/tests
2. https://ci.appveyor.com/project/VlingoNetOwner/vlingo-net-actors/builds/21000810/tests

[tjaskula]

This could be resolved with #29

[tjaskula]

Issue seems to be still there. Sometimes tests fails randomly or don't finish withing 1h execution time.

1. https://ci.appveyor.com/project/VlingoNetOwner/vlingo-net-actors/builds/22567843/tests

[VaughnVernon]

@tjaskula Tests should be rewritten to use AccessSafely.

[tjaskula]

Fixed with new implementation and AccessSafely

[tjaskula]

Reopening with some new cases

[xUnit.net 00:00:37.65]     Vlingo.Actors.Tests.Supervision.CommonSupervisionTest.TestPongSupervisor [FAIL]
686Test run in progress.                                                                                                                                                                                                                                                            X Vlingo.Actors.Tests.Supervision.CommonSupervisionTest.TestPongSupervisor [372ms]
687  Error Message:
688   Assert.Equal() Failure
689Expected: 11
690Actual:   10
691  Stack Trace:
692     at Vlingo.Actors.Tests.Supervision.CommonSupervisionTest.TestPongSupervisor() in /home/appveyor/projects/vlingo-net-actors/src/Vlingo.Actors.Tests/Supervision/CommonSupervisionTest.cs:line 95
693Test run in progress.......                                                                                                                                                                                                                                                          [xUnit.net 00:00:44.37]     Vlingo.Actors.Tests.CompletesActorProtocolTest.TestThatTimeOutOccursForSideEffects [FAIL]
694Test run in progress.                                                                                                                                                                                                                                                            X Vlingo.Actors.Tests.CompletesActorProtocolTest.TestThatTimeOutOccursForSideEffects [198ms]
695  Error Message:
696   Assert.NotEqual() Failure
697Expected: Not "Hello, Completes!"
698Actual:   "Hello, Completes!"
699  Stack Trace:
700     at Vlingo.Actors.Tests.CompletesActorProtocolTest.TestThatTimeOutOccursForSideEffects() in /home/appveyor/projects/vlingo-net-actors/src/Vlingo.Actors.Tests/CompletesActorProtocolTest.cs:line 88

[tjaskula]

Also freezes TestPublicRootDefaultParentSupervisor