Add empty config value for scope based config setting (#5551)

Author: sureshanaparti

server/src/main/java/com/cloud/configuration/ConfigurationManagerImpl.java

@@ -826,12 +826,6 @@ public Configuration updateConfiguration(final UpdateCfgCmd cmd) throws InvalidP
             return _configDao.findByName(name);
         }
 
-        value = value.trim();
-
-        if (value.isEmpty() || value.equals("null")) {
-            value = null;
-        }
-
         String scope = null;
         Long id = null;
         int paramCountCheck = 0;
@@ -871,6 +865,12 @@ public Configuration updateConfiguration(final UpdateCfgCmd cmd) throws InvalidP
             throw new InvalidParameterValueException("cannot handle multiple IDs, provide only one ID corresponding to the scope");
         }
 
+        value = value.trim();
+
+        if (value.isEmpty() || value.equals("null")) {
+            value = (id == null) ? null : "";
+        }
+
         final String updatedValue = updateConfiguration(userId, name, catergory, value, scope, id);
         if (value == null && updatedValue == null || updatedValue.equalsIgnoreCase(value)) {
             return _configDao.findByName(name);