Making Watcher disabled by default for Monitoring Integration tests

Some tests [reasonably] fail due to unexpected indices appearing in the cluster due to Watcher.

- Also had to reset shieldEnabled as a static field, which makes no sense, but tests were failing unpredictably without it
    - Now they're passing unpredictably with it... will investigate

Original commit: elastic/x-pack-elasticsearch@9b6ce681d8

elasticsearch/x-pack/marvel/src/test/java/org/elasticsearch/marvel/agent/resolver/node/NodeStatsTests.java

@@ -96,4 +96,11 @@ public class NodeStatsTests extends MarvelIntegTestCase {
 
         return Arrays.stream(NodeStatsResolver.FILTERS).filter(s -> s.contains("watcher") == false).toArray(String[]::new);
     }
+
+    @Override
+    protected boolean enableWatcher() {
+        // currently this is the only Monitoring test that expects Watcher to be enabled.
+        // Once this becomes the default, then this should be removed.
+        return randomBoolean();
+    }
 }

elasticsearch/x-pack/marvel/src/test/java/org/elasticsearch/marvel/test/MarvelIntegTestCase.java

@@ -73,11 +73,12 @@ public abstract class MarvelIntegTestCase extends ESIntegTestCase {
      * <p>
      * Control this by overriding {@link #enableShield()}, which defaults to enabling it randomly.
      */
-    protected Boolean shieldEnabled;
+    // SCARY: This needs to be static or lots of tests randomly fail, but it's not used statically!
+    protected static Boolean shieldEnabled;
     /**
      * Enables individual tests to control the behavior.
      * <p>
-     * Control this by overriding {@link #enableWatcher()}, which defaults to enabling it randomly.
+     * Control this by overriding {@link #enableWatcher()}, which defaults to disabling it (this will change!).
      */
     protected Boolean watcherEnabled;
 
@@ -89,8 +90,10 @@ public abstract class MarvelIntegTestCase extends ESIntegTestCase {
         if (watcherEnabled == null) {
             watcherEnabled = enableWatcher();
         }
-        logger.info("--> shield {}", shieldEnabled ? "enabled" : "disabled");
+
+        logger.debug("--> shield {}", shieldEnabled ? "enabled" : "disabled");
         logger.debug("--> watcher {}", watcherEnabled ? "enabled" : "disabled");
+
         return super.buildTestCluster(scope, seed);
     }
 
@@ -174,7 +177,9 @@ public abstract class MarvelIntegTestCase extends ESIntegTestCase {
      * Override and return {@code false} to force running without Watcher.
      */
     protected boolean enableWatcher() {
-        return randomBoolean();
+        // Once randomDefault() becomes the default again, then this should only be actively disabled when
+        // trying to figure out exactly how many indices are at play
+        return false;
     }
 
     protected void stopCollection() {