PingFederate SP SLO not going to IDP - pingfederate

Question

We are using PingFederate as an SP and have configured opentokenadapter. We are also using PingFederate Apache Agent (mod_pf.so) for SSO. When the user is clicking on logout link below steps are happening:
Call goes to the logout url defined in mod_pf.conf file (PingFederateCancelURL) This is our application logout page.
Another call goes to /sp/startSLO.png and I can see SLO logs in the pingfederate server.
However there is no call going to IDP configured for this connection. Are we missing any configuration?
P.S. We have not configured Logout Service in the opentoken adapter configuration.
Adding Logs:
2016-06-13 03:01:36,128 tid:C0aV2SqcQXoy97ployGFLFGFR14 DEBUG [org.sourceid.websso.servlet.IntegrationControllerServlet] GET: https://ny-pingfed-app02.na.rtdom.net:9031/sp/startSLO.ping
2016-06-13 03:01:36,128 tid:C0aV2SqcQXoy97ployGFLFGFR14 DEBUG [org.sourceid.saml20.service.impl.grouprpc.PreferredNodes] [] -> indices to addresses -> [10.221.56.36:7600, 10.221.56.29:7600]
2016-06-13 03:01:36,128 DEBUG [com.pingidentity.jgroups.MuxInvocationHandler] invocation of lookupAuthnBeansAndSessions on org.sourceid.saml20.service.impl.localmemory.SpSessionRegistryMapImpl#7a85063c{bean->session=19, nidKey->sessionlists=7, pfsessionid->beanslist=17} w/args: [oYxtMFSy5GYQ5lK3EN1Lkt] returned {SpHashableAuthnBean: 8b3ec7801a2976aa103df829dffc21f260ea7aca=WebSsoSession{entityId='https://devci-casshib-ny.mediaocean.com/idp/shibboleth', assertionId='_36dab27f092d6367407cb9042e350aed', sessionIndex='_0d66d53a8fea5733ea5621a7b90b923b', nameId(value)=_3aa309b361c657bf1bc2a307d19ac432}}
2016-06-13 03:01:36,131 tid:C0aV2SqcQXoy97ployGFLFGFR14 DEBUG [org.sourceid.saml20.service.impl.grouprpc.SpSessionRegistryGroupRpcImpl] called mode:GET_MAJORITY lookupAuthnBeansAndSessions([oYxtMFSy5GYQ5lK3EN1Lkt]) on [10.221.56.36:7600, 10.221.56.29:7600] responses:
[sender=10.221.56.36:7600, retval={SpHashableAuthnBean: 8b3ec7801a2976aa103df829dffc21f260ea7aca=WebSsoSession{entityId='https://devci-casshib-ny.mediaocean.com/idp/shibboleth', assertionId='_36dab27f092d6367407cb9042e350aed', sessionIndex='_0d66d53a8fea5733ea5621a7b90b923b', nameId(value)=_3aa309b361c657bf1bc2a307d19ac432}}, received=true, suspected=false]
[sender=10.221.56.29:7600, retval={SpHashableAuthnBean: 8b3ec7801a2976aa103df829dffc21f260ea7aca=WebSsoSession{entityId='https://devci-casshib-ny.mediaocean.com/idp/shibboleth', assertionId='_36dab27f092d6367407cb9042e350aed', sessionIndex='_0d66d53a8fea5733ea5621a7b90b923b', nameId(value)=_3aa309b361c657bf1bc2a307d19ac432}}, received=true, suspected=false]
2016-06-13 03:01:36,131 tid:C0aV2SqcQXoy97ployGFLFGFR14 DEBUG [org.sourceid.saml20.service.impl.grouprpc.PreferredNodes] [] -> indices to addresses -> [10.221.56.36:7600, 10.221.56.29:7600]
2016-06-13 03:01:36,131 tid:C0aV2SqcQXoy97ployGFLFGFR14 DEBUG [org.sourceid.saml20.service.impl.grouprpc.SpSessionRegistryGroupRpcImpl] called mode:GET_NONE unregisterSessionsReceived([[SpHashableAuthnBean: 8b3ec7801a2976aa103df829dffc21f260ea7aca]]) on [10.221.56.36:7600, 10.221.56.29:7600]
2016-06-13 03:01:36,230 DEBUG [com.pingidentity.jgroups.MuxInvocationHandler] invocation of unregisterSessionsReceived on org.sourceid.saml20.service.impl.localmemory.SpSessionRegistryMapImpl#7a85063c{bean->session=18, nidKey->sessionlists=6, pfsessionid->beanslist=16} w/args: [[SpHashableAuthnBean: 8b3ec7801a2976aa103df829dffc21f260ea7aca]] returned null
2016-06-13 03:01:36,263 tid:C0aV2SqcQXoy97ployGFLFGFR14 DEBUG [org.sourceid.util.log.internal.TrackingIdSupport] [cross-reference-message] PFSessionXRefID:_0d66d53a8fea5733ea5621a7b90b923b
2016-06-13 03:01:36,501 WARN [org.eclipse.jetty.servlet.ServletHandler]
javax.servlet.ServletException: org.sourceid.websso.profiles.ProcessRuntimeException: org.sourceid.saml20.adapter.AuthnAdapterException: Logout functionality invoked, but no logout service is configured for this adapter.
at org.sourceid.servlet.ServletExceptionSupport.throwServletException(ServletExceptionSupport.java:26)
at org.sourceid.websso.servlet.IntegrationControllerServlet.process(IntegrationControllerServlet.java:88)
at org.sourceid.websso.servlet.EnforcerServletBase.checkProcess(EnforcerServletBase.java:84)
It seems that Logout Service is mandatory parameter. What should be it's value? Should it be IDP's SLO endpoint or application's (which SP is protecting) logout url?