ONOS-3411 Disconnect switches and stop stat collectors when openflow-base is being deactivated

Change-Id: I9a1b5fbb60a9e7135cd586fe717c18f83e3d864d
diff --git a/providers/openflow/meter/src/main/java/org/onosproject/provider/of/meter/impl/OpenFlowMeterProvider.java b/providers/openflow/meter/src/main/java/org/onosproject/provider/of/meter/impl/OpenFlowMeterProvider.java
index f5a777b..e411379 100644
--- a/providers/openflow/meter/src/main/java/org/onosproject/provider/of/meter/impl/OpenFlowMeterProvider.java
+++ b/providers/openflow/meter/src/main/java/org/onosproject/provider/of/meter/impl/OpenFlowMeterProvider.java
@@ -132,6 +132,8 @@
     @Deactivate
     public void deactivate() {
         providerRegistry.unregister(this);
+        collectors.values().forEach(MeterStatsCollector::stop);
+        collectors.clear();
         controller.removeEventListener(listener);
         controller.removeListener(listener);
         providerService = null;