Junit Tests in nuxeo-core-redis bundle should be ignored if there is no Redis running

Discovered while building nuxeo-core on JenkinsX:

Failures because:

java.lang.AssertionError: invoke on features error [Holder [type=class org.nuxeo.runtime.test.runner.MDCFeature], Holder [type=class org.nuxeo.runtime.test.runner.ConditionalIgnoreRule$Feature], Holder [type=class org.nuxeo.runtime.test.runner.RandomBug$Feature], Holder [type=class org.nuxeo.runtime.test.runner.RuntimeFeature], Holder [type=class org.nuxeo.runtime.test.runner.TransactionalFeature], Holder [type=class org.nuxeo.runtime.stream.RuntimeStreamFeature], Holder [type=class org.nuxeo.ecm.core.work.WorkManagerFeature], Holder [type=class org.nuxeo.ecm.core.io.CoreIOFeature], Holder [type=class org.nuxeo.ecm.core.bulk.CoreBulkFeature], Holder [type=class org.nuxeo.ecm.core.test.CoreFeature], Holder [type=class org.nuxeo.ecm.core.redis.RedisFeature]]

–
Suppressed: java.lang.NullPointerException
at org.nuxeo.ecm.core.redis.RedisComponent.clear(RedisComponent.java:98)
at org.nuxeo.ecm.core.redis.RedisFeature.beforeRun(RedisFeature.java:152)
at org.nuxeo.runtime.test.runner.FeaturesRunner.lambda$beforeRun$1(FeaturesRunner.java:155)
at org.nuxeo.runtime.test.runner.FeaturesLoader.apply(FeaturesLoader.java:126)

See failures here:
http://jenkins.l2it.35.231.200.170.nip.io/job/nuxeo-sandbox/job/nuxeo/job/master/59/