Gitlab ci fixes

[atomfrede]

• Correct gatling report path for maven
• Don't do nom-install when client was skipped
• Don't try to cache maven files when using gradle and vice versa

Examples can be found here:

• https://gitlab.com/atomfrede/jhipster-ci-example-maven
• https://gitlab.com/atomfrede/jhipster-ci-example-gradle

[pascalgrimaud]

Thanks again @atomfrede I should have time to test everything this weekend or next week, and made a new release!