Management::get method does not reflect maskable configs

This is modified from the existing test.
```java
@Test
public void updateConfigurationTest() throws Exception {
final MapConfiguration graphConfig = getGraphConfig();
final String graphName = graphConfig.getString(GRAPH_NAME.toStringWithoutRoot());

try {
ConfiguredGraphFactory.createConfiguration(graphConfig);
final StandardJanusGraph graph = (StandardJanusGraph) ConfiguredGraphFactory.open(graphName);
assertNotNull(graph);

final Map map = graphConfig.getMap();
map.put("query.batch", true);
ConfiguredGraphFactory.updateConfiguration(graphName, ConfigurationUtil.loadMapConfiguration(map));
assertNull(gm.getGraph(graphName));

JanusGraph graph2 = ConfiguredGraphFactory.open(graphName);
// THIS FAILS! It still returns the default value, false
assertEquals("true", graph2.openManagement().get("query.batch"));
} finally {
ConfiguredGraphFactory.removeConfiguration(graphName);
ConfiguredGraphFactory.close(graphName);
}
}
```

Compared to the existing test (that is passing!) where we modify https://github.com/JanusGraph/janusgraph/blob/ba93c4bfda9e4c72b01aae7dc2ee9c3c5b5f37d1/janusgraph-backend-testutils/src/main/java/org/janusgraph/core/AbstractConfiguredGraphFactoryTest.java#L228 in the above example, we modify `query.batch` option. Somehow the change is not reflected.

Start with updateConfigurationTest in janusgraph-backend-testutils/src/main/java/org/janusgraph/core/AbstractConfiguredGraphFactoryTest.java and reproduce the query.batch case described in the issue. Trace how ConfiguredGraphFactory.updateConfiguration and Management::get handle that configuration, then make the test pass with the updated value reflected instead of the default false.

Written by the indexing model from the issue text.