Stop running the unreliable known hosts test on ci.jenkins.io

Not valuable enough to deal with the disruption of unreliable tests.
Tests are run regularly in my CI environment without issue and they are
run by every developer that executes the tests.

(cherry picked from commit c876c16)

Author: MarkEWaite

src/test/java/org/jenkinsci/plugins/gitclient/verifier/KnownHostsTestUtil.java

@@ -153,12 +153,9 @@ public static String nonGitHubHost() {
 
     /* Return true if known hosts tests should be run in this context */
     public static boolean runKnownHostsTests() {
-        if (!JENKINS_URL.contains("ci.jenkins.io")) {
-            /* Always run the tests if not on ci.jenkins.io */
-            return true;
-        }
-        // Only test 10% of the time on ci.jenkins.io to reduce load on ssh providers
-        return ThreadLocalRandom.current().nextInt(10) == 0;
+        /* Run the problematic known hosts tests on all locations except ci.jenkins.io */
+        /* Do not run the problematic known hosts tests on ci.jenkins.io, they are unreliable */
+        return !JENKINS_URL.contains("ci.jenkins.io");
     }
 
     /* Always return false, retained for test compatibility */