Fix importing unmanaged instances due to incorrect internal name (#11753)

diff --git a/server/src/main/java/org/apache/cloudstack/vm/UnmanagedVMsManagerImpl.java b/server/src/main/java/org/apache/cloudstack/vm/UnmanagedVMsManagerImpl.java
index 30cf4ad..e5eb29a 100644
--- a/server/src/main/java/org/apache/cloudstack/vm/UnmanagedVMsManagerImpl.java
+++ b/server/src/main/java/org/apache/cloudstack/vm/UnmanagedVMsManagerImpl.java
@@ -1128,7 +1128,7 @@
         }
 
         String internalCSName = unmanagedInstance.getInternalCSName();
-        if (StringUtils.isEmpty(instanceNameInternal)) {
+        if (StringUtils.isEmpty(internalCSName)) {
             internalCSName = instanceNameInternal;
         }
         Map<String, String> allDetails = new HashMap<>(details);