Fix issues observed while testing b03702 concurrency and thread safety

[kaladay]

This does not resolve b03702, but does upgrade unit testing such that some amount of concurrency testing may be performed.

Junit 5.3 (junit jupiter) is now used. It is fully backwards compatible with Junit 4 such that existing tests need not be upgraded. In this case, existing tests have been upgraded from Junit 4 to Junit 5.

An example configuration for concurrency testing may be found in the pom.xml under maven-surefire-plugin.

IRContext is trying to remove a triple when calling removeVersion() instead of a version.

Remove unused ObjectMapper from IRContextTransactionController.

AppUserCredentialsService implementation is backported from Project Management Service to fix NULL errors that are exposed during concurrency testing.

User model's setRole() needs to handle NULL role parameter (issue exposed during concurrency testing).

[coveralls]

Coverage increased (+6.2%) to 33.333% when pulling 987690a109fd6938db91ac5024ae1bdb50ae72eb on dame-sprint-dec-b03702-concurrency_and_thread_safety into acf1c7aeecea6f64c400eb8ec468e84b2f861264 on dame-sprint-dec-staging.