Fixes after adding UBI Docker support

The CertGenCliTests needed an update to ignore the UBI Docker
distribution as well as the regular Docker distribution.

qa/os/src/test/java/org/elasticsearch/packaging/test/CertGenCliTests.java

@@ -50,7 +50,7 @@ public class CertGenCliTests extends PackagingTestCase {
     @Before
     public void filterDistros() {
         assumeTrue("only default distro", distribution.flavor == Distribution.Flavor.DEFAULT);
-        assumeTrue("no docker", distribution.packaging != Distribution.Packaging.DOCKER);
+        assumeFalse("no docker", distribution.isDocker());
     }
 
     @BeforeClass