fix incorrect iscsi path stat for managed storage (#3181)

## Description
The issue was that an Incorrect iscsi path was being passed for managed storage pools when collecting volume stats. Storage pools normally have a UUID based path while managed storage pools require an IQN based path

Author: skattoju3

server/src/main/java/com/cloud/server/StatsCollector.java

@@ -928,7 +928,11 @@ protected void runInContext() {
                     List<String> volumeLocators = new ArrayList<String>();
                     for (VolumeVO volume : volumes) {
                         if (volume.getFormat() == ImageFormat.QCOW2) {
-                            volumeLocators.add(volume.getUuid());
+                            if (pool.isManaged()) {
+                                volumeLocators.add(volume.getPath());
+                            } else {
+                                volumeLocators.add(volume.getUuid());
+                            }
                         } else if (volume.getFormat() == ImageFormat.VHD) {
                             volumeLocators.add(volume.getPath());
                         } else if (volume.getFormat() == ImageFormat.OVA) {