Remove configmgr multiSlave references

Remove references to multiSlave attribute in ConfigMgr code. Xsl references have not been removed as comments mention backward compatibility.

Fixes gh-1742

Signed-off-by: Sridhar Meda <sridhar.meda@lexisnexis.com>

deployment/deployutils/configenvhelper.cpp

@@ -1249,7 +1249,6 @@ void CConfigEnvHelper::UpdateThorAttributes(IPropertyTree* pParentNode)
         }
     }
 
-    setAttribute(pParentNode, XML_ATTR_MULTISLAVES, multiSlaves ? "true" : "false");
     setAttribute(pParentNode, "@localThor", localThor ? "true" : "false");
 }