NXCM-4928: Bump to JUnit 4.11

Depends on following pulls:
https://github.com/sonatype/sisu-litmus/pull/16
https://github.com/sonatype/http-testing-harness/pull/2

Mostly:
* POM changes regarding litmus and HTH versions
* POM changes regarding enforcer rules banning junit:junit and junit:junit-dep
* slight (needed) changes in one UT class (new in JUnit 4.11: ExceptionRule does not handle AssertionError anymore unless explicitly told to do so)

CI:
until those pulls above are not merged and built by CI, this branch will not build properly.

Related issue:
https://issues.sonatype.org/browse/NXCM-4928