STC fixes

- NPE when a switch has already been removed and an attempt is made
  to access stats on the switch.

- NPE in group provider if the system is in the process of shutting down.

- Lower ERROR to WARN when switch resources are not available.

Change-Id: I5b90ff328b19c2d661fde3a24e90614999c4c900

@@ -159,7 +159,7 @@ final class ResourceDeviceListener implements DeviceListener {
                 .map(adminService::register)
                 .ifPresent(success -> {
                    if (!success) {
-                       log.error("Failed to register Bandwidth for {}", portPath.id());
+                       log.warn("Failed to register Bandwidth for {}", portPath.id());
                    }
                 });
 

@@ -269,6 +269,10 @@ public class OpenFlowRuleProvider extends AbstractProvider
         Dpid dpid = Dpid.dpid(flowRule.deviceId().uri());
         OpenFlowSwitch sw = controller.getSwitch(dpid);
 
+        if (sw == null) {
+            return;
+        }
+
         FlowRuleExtPayLoad flowRuleExtPayLoad = flowRule.payLoad();
         if (hasPayload(flowRuleExtPayLoad)) {
             OFMessage msg = new ThirdPartyMessage(flowRuleExtPayLoad.payLoad());
@@ -298,6 +302,10 @@ public class OpenFlowRuleProvider extends AbstractProvider
         Dpid dpid = Dpid.dpid(flowRule.deviceId().uri());
         OpenFlowSwitch sw = controller.getSwitch(dpid);
 
+        if (sw == null) {
+            return;
+        }
+
         FlowRuleExtPayLoad flowRuleExtPayLoad = flowRule.payLoad();
         if (hasPayload(flowRuleExtPayLoad)) {
             OFMessage msg = new ThirdPartyMessage(flowRuleExtPayLoad.payLoad());

@@ -211,7 +211,7 @@ public class OpenFlowGroupProvider extends AbstractProvider implements GroupProv
             }
         }
 
-        if (groupStatsReply != null && groupDescStatsReply != null) {
+        if (providerService != null && groupStatsReply != null) {
             Collection<Group> groups = buildGroupMetrics(deviceId,
                     groupStatsReply, groupDescStatsReply);
             providerService.pushGroupMetrics(deviceId, groups);