gss: register GSS_KRB5_S error table

The Kerberos GSS mechanism specific error table in gkrb5_err.et was never
registered with libkrb5, so the messages corresponding to those errors would
never be available. Register them with the thread local context used by the
krb5 mechanism.

lib/gssapi/krb5/init.c

@@ -69,6 +69,7 @@ _gsskrb5_init (krb5_context *context)
 
 	ret = krb5_init_context(context);
 	if (ret == 0) {
+	    krb5_add_et_list(*context, initialize_gk5_error_table_r);
 	    HEIMDAL_setspecific(context_key, *context, ret);
 	    if (ret) {
 		krb5_free_context(*context);