[2.11.x] Allow specifying of bundle to be used by modern ITs via system property

This allows running ITs agains a bundle zip. E.g.

mvn clean install -pl testsuite/modern-testsuite/ -Pit -Dit.test=SmokeIT -Dit.nexus.bundle=./nexus-2.10.0-01-bundle.zip

Also dropped parameters from all IT that were overriding the default set of parameters.