[CI] gitlab-ci can now use variable 'JENKINS_FAIL_MODE' to specify the behaviour depending on test results:

JENKINS_FAIL_MODE can be optionally defined as secret variable in the gitlab project CI/CD settings
as comma-separated list of one or more of the following modes:
 - 'FAIL' : fail in case any test has failed
 - 'SKIP' : fail in case any test wad skiped
 - 'NO_TEST' : fail in case no test was run
If multiple modes are specified, fail if any of them occurs.
If none specified (or JENKINS_FAIL_MODE not defined) the job will ignore test results.