Fix errors in functional tests logs

Updated T&P, following NXP-27443 changes, shows errors in server.log for:

• Kerberos

  20:33:34 /opt/jenkins/workspace/TestAndPush/ondemand-testandpush-check-master/ftests/nuxeo-kerberos-authentication-ftests/target/tomcat/log/server.log:
  20:33:34 2020-03-30T18:26:28,828 ERROR [main] [org.nuxeo.ecm.platform.ui.web.auth.krb5.Krb5Authenticator] Cannot create LoginContext, disabling Kerberos module
  

• WOPI

  20:33:35 /opt/jenkins/workspace/TestAndPush/ondemand-testandpush-check-master/ftests/nuxeo-wopi-ftests/target/tomcat/log/server.log:
  20:33:35 2020-03-30T18:52:10,654 ERROR [main] [org.nuxeo.wopi.WOPIServiceImpl] Cannot load WOPI discovery: WOPI disabled
  

Both should be WARN logs as they are expected cases.