HDDS-957. Replace incorrect use of system property user.name.

Contributed by Dinesh Chitlangia.

hadoop-ozone/ozone-manager/src/main/java/org/apache/hadoop/ozone/web/ozShell/volume/CreateVolumeHandler.java

@@ -79,7 +79,7 @@ public class CreateVolumeHandler extends Handler {
     if (root) {
       rootName = "hdfs";
     } else {
-      rootName = System.getProperty("user.name");
+      rootName = UserGroupInformation.getCurrentUser().getShortUserName();
     }
 
     VolumeArgs.Builder volumeArgsBuilder = VolumeArgs.newBuilder()

hadoop-ozone/ozone-manager/src/main/java/org/apache/hadoop/ozone/web/ozShell/volume/ListVolumeHandler.java

@@ -31,6 +31,7 @@ import org.apache.hadoop.ozone.web.ozShell.OzoneAddress;
 import org.apache.hadoop.ozone.web.ozShell.Shell;
 import org.apache.hadoop.ozone.web.utils.JsonUtils;
 
+import org.apache.hadoop.security.UserGroupInformation;
 import picocli.CommandLine.Command;
 import picocli.CommandLine.Option;
 import picocli.CommandLine.Parameters;
@@ -76,7 +77,7 @@ public class ListVolumeHandler extends Handler {
     OzoneClient client = address.createClient(createOzoneConfiguration());
 
     if (userName == null) {
-      userName = System.getProperty("user.name");
+      userName = UserGroupInformation.getCurrentUser().getShortUserName();
     }
 
     if (maxVolumes < 1) {