Fix non working update dynamic settings

Described in elastic/elasticsearch#10614, it's not possible with cloud discovery plugin to update dynamic settings anymore.

```sh
curl -XPUT localhost:9200/_cluster/settings -d '{
    "persistent" : {
        "discovery.zen.minimum_master_nodes" : 3
    },
    "transient" : {
        "discovery.zen.minimum_master_nodes" : 3
    }
}'
```

gives

```json
{"acknowledged":true,"persistent":{},"transient":{}}
```

Closes #47.

(cherry picked from commit 9df33a3)
(cherry picked from commit a40016e)

Author: dadoonet

src/main/java/org/elasticsearch/discovery/gce/GceDiscovery.java

@@ -24,6 +24,7 @@
 import org.elasticsearch.cluster.ClusterName;
 import org.elasticsearch.cluster.ClusterService;
 import org.elasticsearch.cluster.node.DiscoveryNodeService;
+import org.elasticsearch.cluster.settings.ClusterDynamicSettings;
 import org.elasticsearch.cluster.settings.DynamicSettings;
 import org.elasticsearch.common.collect.ImmutableList;
 import org.elasticsearch.common.inject.Inject;
@@ -49,7 +50,7 @@ public GceDiscovery(Settings settings, ClusterName clusterName, ThreadPool threa
                         ClusterService clusterService, NodeSettingsService nodeSettingsService, ZenPingService pingService,
                         DiscoveryNodeService discoveryNodeService, GceComputeService gceComputeService,
                         NetworkService networkService, DiscoverySettings discoverySettings,
-                        ElectMasterService electMasterService, DynamicSettings dynamicSettings,
+                        ElectMasterService electMasterService, @ClusterDynamicSettings DynamicSettings dynamicSettings,
                         Version version) {
         super(settings, clusterName, threadPool, transportService, clusterService, nodeSettingsService,
                 discoveryNodeService, pingService, electMasterService, discoverySettings, dynamicSettings);