Initialize life/rlife in kdcpolicy interface

A value of 0 indicates that the plugin doesn't wish to modify lifetimes.
Make this the default, rather than requiring all plugins to set these
values themselves.

(cherry picked from commit d81c587)

ticket: 8824
version_fixed: 1.17.1

src/kdc/policy.c

@@ -106,7 +106,7 @@ check_kdcpolicy_as(krb5_context context, const krb5_kdc_req *request,
                    krb5_data *const *auth_indicators, krb5_timestamp kdc_time,
                    krb5_ticket_times *times, const char **status)
 {
-    krb5_deltat life, rlife;
+    krb5_deltat life = 0, rlife = 0;
     krb5_error_code ret;
     kdcpolicy_handle *hp, h;
     char **ais = NULL;
@@ -146,7 +146,7 @@ check_kdcpolicy_tgs(krb5_context context, const krb5_kdc_req *request,
                     krb5_data *const *auth_indicators, krb5_timestamp kdc_time,
                     krb5_ticket_times *times, const char **status)
 {
-    krb5_deltat life, rlife;
+    krb5_deltat life = 0, rlife = 0;
     krb5_error_code ret;
     kdcpolicy_handle *hp, h;
     char **ais = NULL;