1) I have referred the blog on http://www.apiman.io/blog/gateway/security/oauth2/keycloak/authentication/authorization/1.2.x/2016/01/22/keycloak-oauth2-redux.html for using the keycloak oauth2 policy.
2) There is one field as forward keycloak token information in keycloak oauth2 policy. I have added the header as X-AZP and field as azp in forward keycloak token information field.
3) Still I am unable to get the header as X-AZP when requested with the api url in apiman.