CLOUD-468 upgrade gradle version to 2.3

[oleewere]

@doktoric

• upgraded gradle version to 2.3
• remove unused systemProperties (this field also not supported in version 2.3)
• jacoco test properties cannot be set at sonarRunner -> relocate into test task

[jenkins-cloudbreak]

Jenkins build finished, all tests passed. Refer to this link for build results: http://ci.sequenceiq.com/job/cloudbreak-shell-pull-request/37/