Log Viewer fails to open logs with error "HTTP Status 409 - Invalid credentials to view log files"

Issue

Cannot select the machine for viewing log file on the Log Viewer, with following error:

JBWEB000065: HTTP Status 409 - Invalid credentials to view log files. Must be superuser.

Checking `/var/log/ovirt-engine/server.log:

2016-04-04 12:06:11,684 INFO  [com.redhat.gss.redhat_access_plugin.server.api_interraction.ApiInterraction] (ajp-/127.0.0.1:8702-11) Querying https://FQDN/ovirt-engine/api/hosts/ with JSESSIONID=VMS8kcd1DU6Ez4L49dJtiRzx
2016-04-04 12:06:11,700 INFO  [com.redhat.gss.redhat_access_plugin.server.filters.SessionFilter] (ajp-/127.0.0.1:8702-11) Adding cookies and headers JSESSIONID=VMS8kcd1DU6Ez4L49dJtiRzx
2016-04-04 12:06:11,797 ERROR [com.redhat.gss.redhat_access_plugin.server.api_interraction.ApiInterraction] (ajp-/127.0.0.1:8702-11) javax.ws.rs.ProcessingException: Unable to invoke request
2016-04-04 12:06:11,797 ERROR [com.redhat.gss.redhat_access_plugin.server.Machines] (ajp-/127.0.0.1:8702-11) Error while retrieving hosts: Unable to invoke request
2016-04-04 12:06:11,797 INFO  [com.redhat.gss.redhat_access_plugin.server.Machines] (ajp-/127.0.0.1:8702-11) System List: [RHEV Manager]
2016-04-04 12:06:16,235 INFO  [com.redhat.gss.redhat_access_plugin.server.api_interraction.ApiInterraction] (ajp-/127.0.0.1:8702-16) Querying https://FQDN/ovirt-engine/api/users/fdfc627c-d875-11e0-90f0-83df133b58cc/roles with JSESSIONID=VMS8kcd1DU6Ez4L49dJtiRzx
2016-04-04 12:06:16,236 INFO  [com.redhat.gss.redhat_access_plugin.server.filters.SessionFilter] (ajp-/127.0.0.1:8702-16) Adding cookies and headers JSESSIONID=VMS8kcd1DU6Ez4L49dJtiRzx
2016-04-04 12:06:16,284 ERROR [com.redhat.gss.redhat_access_plugin.server.api_interraction.ApiInterraction] (ajp-/127.0.0.1:8702-16) javax.ws.rs.ProcessingException: Unable to invoke request
2016-04-04 12:06:16,284 ERROR [com.redhat.gss.redhat_access_plugin.server.Logs] (ajp-/127.0.0.1:8702-16) Invalid credentials to view log files.  Must be superuser.