backup(nas): wrapper uses the passed bitmap name instead of re-parsing it

The BITMAP_CREATED line is only a success signal (the bitmap genuinely isn't
created for stopped-VM RBD/LINSTOR sources); its value is the same --bitmap-new
we passed in, so use command.getBitmapNew() rather than re-parsing the echoed
value. Addresses review comment on #13074 (LibvirtTakeBackupCommandWrapper).

Author: jmsperu

plugins/hypervisors/kvm/src/main/java/com/cloud/hypervisor/kvm/resource/wrapper/LibvirtTakeBackupCommandWrapper.java

@@ -122,7 +122,11 @@ public Answer execute(TakeBackupCommand command, LibvirtComputingResource libvir
         for (String line : stdout.split("\n")) {
             String trimmed = line.trim();
             if (trimmed.startsWith("BITMAP_CREATED=")) {
-                bitmapCreated = trimmed.substring("BITMAP_CREATED=".length());
+                // The marker only confirms the bitmap was actually created on the disks
+                // (it isn't, e.g., for stopped-VM RBD/LINSTOR sources). The name itself is
+                // the value we already passed via --bitmap-new, so use that rather than
+                // re-parsing the echoed value.
+                bitmapCreated = command.getBitmapNew();
                 continue;
             }
             if (trimmed.startsWith("INCREMENTAL_FALLBACK=")) {