1840870 - Error 'Could not check credentials for user' when upgrading HANA using SUM in a distributed environment

Using the lifecycle management perspective in HANA studio to upgrade a HANA system distributed over multiple nodes results in error  'Could not check credentials for user...' after the password of sapadm user has been entered:

The log file /usr/sap/<SID>/SUM/lmtp.log contains the following errors:

com.sap.lm.hana.api.exception.SapHostControlCredentialsException: Could not check credentials provided for user sapadm on host hdbnode
2.corp.
at com.sap.lm.hana.web.pages.SapAdminCredentialsPageImpl.validateAndStoreData(SapAdminCredentialsPageImpl.java:127)
at com.sap.lm.hana.web.servlet.WizardServlet.determineNextPage(WizardServlet.java:160)
at com.sap.lm.hana.web.servlet.WizardServlet.processRequestInternal(WizardServlet.java:110)
at com.sap.lm.hana.web.servlet.WizardServlet.processRequest(WizardServlet.java:83)
at com.sap.lm.hana.web.servlet.LCMUpdateServlet.processRequestInternal(LCMUpdateServlet.java:106)    
at com.sap.lm.hana.web.servlet.LCMUpdateServlet.doPost(LCMUpdateServlet.java:164)   
at javax.servlet.http.HttpServlet.service(HttpServlet.java:755)

Caused by: com.sap.lm.services.hostcontrol.SAPHostControlException: Could not connect to SAP host agent on host hdbnode2.corp. Check t
hat it is running.   
at com.sap.lm.services.hostcontrol.SAPHostControlService.wrapHostControlException(SAPHostControlService.java:204)  
at com.sap.lm.services.hostcontrol.SAPHostControlService.checkUserCredentials(SAPHostControlService.java:399)   
at com.sap.lm.hana.validation.UpdateDataValidatorImpl.checkSapAdmCredentials(UpdateDataValidatorImpl.java:220)    
... 
98 more
Caused by: com.sun.xml.internal.ws.client.ClientTransportException: HTTP transport error: java.net.ConnectException: Connection refused
at com.sun.xml.internal.ws.transport.http.client.HttpClientTransport.getOutput(HttpClientTransport.java:121)      
at com.sun.xml.internal.ws.transport.http.client.HttpTransportPipe.process(HttpTransportPipe.java:142)     
at com.sun.xml.internal.ws.transport.http.client.HttpTransportPipe.processRequest(HttpTransportPipe.java:83)      
at com.sun.xml.internal.ws.transport.DeferredTransportPipe.processRequest(DeferredTransportPipe.java:105) 
at com.sun.xml.internal.ws.api.pipe.Fiber.__doRun(Fiber.java:587) 

Distributed HANA system; Using SUM (Software Update Manager) as outlined in the Automated Update Guide

KBA , HAN-LM-PLT , SAP HANA Platform Lifecycle Management , Problem