Fix JVM GC monitor missing settings test

This commit fixes a test bug in
JvmGcMonitorServiceSettingsTests#testMissingSetting. The purpose of the
test is to test that if settings are provided for a collector for at
least one of warn, info, and debug then it is provided for all of warn,
info, and debug. However, for a collector setting to be valid it must be
a positive time value but the randomization in the test construction
could produce zero time values.

Closes #16369

core/src/test/java/org/elasticsearch/monitor/jvm/JvmGcMonitorServiceSettingsTests.java

@@ -62,9 +62,9 @@ public class JvmGcMonitorServiceSettingsTests extends ESTestCase {
     public void testMissingSetting() throws InterruptedException {
         String collector = randomAsciiOfLength(5);
         Set<AbstractMap.SimpleEntry<String, String>> entries = new HashSet<>();
-        entries.add(new AbstractMap.SimpleEntry<>("monitor.jvm.gc.collector." + collector + ".warn", randomTimeValue()));
-        entries.add(new AbstractMap.SimpleEntry<>("monitor.jvm.gc.collector." + collector + ".info", randomTimeValue()));
-        entries.add(new AbstractMap.SimpleEntry<>("monitor.jvm.gc.collector." + collector + ".debug", randomTimeValue()));
+        entries.add(new AbstractMap.SimpleEntry<>("monitor.jvm.gc.collector." + collector + ".warn", randomPositiveTimeValue()));
+        entries.add(new AbstractMap.SimpleEntry<>("monitor.jvm.gc.collector." + collector + ".info", randomPositiveTimeValue()));
+        entries.add(new AbstractMap.SimpleEntry<>("monitor.jvm.gc.collector." + collector + ".debug", randomPositiveTimeValue()));
         Settings.Builder builder = Settings.builder();
 
         // drop a random setting or two