[WIP] tck multithread failures

[olamy]

• investigate junit5 multi thread build failure Servlet TCK with Jetty
• more thread safe collections
• not sure about those but some thread safe fields

Short description of what this resolves:

Changes proposed in this pull request:

Fixes #

[rhusar]

@olamy Can you link the reproducer?

[olamy]

@olamy Can you link the reproducer?

sure have a look here https://github.com/jetty-project/servlet-tck-run/ use branch jetty-12-ee11-parallel-test

mvn clean verify you may have a lot of download of snapshots, you will have to change the arquillian-core version in the pom. (it's using the version of this PR for testing purpose)

with the current content content of this PR I managed to reduced by a lot failure number because of this change https://github.com/arquillian/arquillian-core/pull/673/files#diff-5c09558098ba87d126edb03750d0b116404b1680a7821a0d206789d58f768d32R12

I still have some errors such

java.lang.NullPointerException: deploymentScenario cannot be null
	at java.base/java.util.Objects.requireNonNull(Objects.java:235)
	at org.jboss.arquillian.container.test.impl.client.ContainerEventController.lookup(ContainerEventController.java:147)
	at org.jboss.arquillian.container.test.impl.client.ContainerEventController.createContext(ContainerEventController.java:133)
	at org.jboss.arquillian.container.test.impl.client.ContainerEventController.createBeforeContext(ContainerEventController.java:117)

note I have added the check here https://github.com/arquillian/arquillian-core/pull/673/files#diff-94ece6fcd6683e6db69d1647fcf29bf2091d8f73deb8dd991848755b646e94d7R147 to track this.

ETA is some random state failures with each builds.