kvm: Strip trailing comma for qemu-img convert options

Fix trailing comma for qemu-img convert options, Qemu 2.0+ not tolerant to it

Signed-off-by: Rohit Yadav <rohit.yadav@shapeblue.com>

plugins/hypervisors/kvm/src/org/apache/cloudstack/utils/qemu/QemuImg.java

@@ -236,6 +236,7 @@ public class QemuImg {
             for (Map.Entry<String, String> option : options.entrySet()) {
                 optionsStr += option.getKey() + "=" + option.getValue() + ",";
             }
+            optionsStr = optionsStr.replaceAll(",$", "");
             s.add(optionsStr);
         }