HPCC-17843 Check DFU queue name correctly in FileSpray web service

The existing FileSpray web service does not read queue names correctly
when a DFU Server has multiple queues.

Signed-off-by: wangkx <kevin.wang@lexisnexis.com>

common/workunit/workunit.cpp

@@ -4764,7 +4764,7 @@ extern WORKUNIT_API void getDFUServerQueueNames(StringArray &ret, const char *pr
     {
         IPropertyTree &target = targets->query();
         if (target.hasProp("@queue"))
-            ret.appendUniq(target.queryProp("@queue"));
+            ret.appendListUniq(target.queryProp("@queue"), ",");
     }
     return;
 }