MDL-12858 fix print_error() usage.

print_error()'s third parameter is the URL we jump to (defaults to
$CFG->wwwroot if not set) when we click the 'Continue' button, not the message
string parameter object.

Forward ported from MOODLE_18_STABLE

auth/ldap/auth.php

@@ -144,7 +144,7 @@ class auth_plugin_ldap extends auth_plugin_base {
         }
         else {
             @ldap_close($ldapconnection);
-            print_error('auth_ldap_noconnect','auth',$this->config->host_url);
+            print_error('auth_ldap_noconnect','auth','',$this->config->host_url);
         }
         return false;
     }
@@ -859,7 +859,7 @@ class auth_plugin_ldap extends auth_plugin_base {
         $user = get_record('user', 'username', $username, 'mnethostid', $CFG->mnet_localhost_id);
         if (empty($user)) { // trouble
             error_log("Cannot update non-existent user: ".stripslashes($username));
-            print_error('auth_dbusernotexist','auth',$username);
+            print_error('auth_dbusernotexist','auth','',$username);
             die;
         }
 
@@ -1585,7 +1585,7 @@ class auth_plugin_ldap extends auth_plugin_base {
         }
 
         //If any of servers are alive we have already returned connection
-        print_error('auth_ldap_noconnect_all','auth',$this->config->user_type);
+        print_error('auth_ldap_noconnect_all','auth','', $debuginfo);
         return false;
     }