MDEV-30318 : galera error messages in mariadb log without galera enabled

Do not compile wsrep_provider plugin if WITH_WSREP is not enabled.
We should not enable wsrep_provider plugin if WSREP_ON=OFF and
at that case we can only print information that Plugin
'wsrep-provider' is disabled.

Make sure tests require Galera library 26.4.14 if needed.

mysql-test/suite/wsrep/r/wsrep_provider_plugin.result

+# Correct Galera library found
 CREATE TABLE t1 (f1 INT PRIMARY KEY) ENGINE=InnoDB;
 SET GLOBAL wsrep_provider_repl_max_ws_size=1;
 SHOW VARIABLES LIKE 'wsrep_provider_repl_max_ws_size';

mysql-test/suite/wsrep/r/wsrep_provider_plugin_basic.result

+# Correct Galera library found
 select variable_type, global_value from information_schema.system_variables where variable_name = 'wsrep_provider_socket_recv_buf_size';
 variable_type	global_value
 VARCHAR	auto

mysql-test/suite/wsrep/r/wsrep_provider_plugin_wsrep_off.result

+SELECT @@wsrep_on;
+@@wsrep_on
+0
+select variable_type, global_value from information_schema.system_variables where variable_name = 'wsrep_provider%';
+variable_type	global_value

mysql-test/suite/wsrep/t/wsrep_provider_plugin.test

@@ -6,6 +6,9 @@
 --source include/have_wsrep.inc
 --source include/have_innodb.inc
 
+--let $galera_version=26.4.14
+source include/check_galera_version.inc;
+
 CREATE TABLE t1 (f1 INT PRIMARY KEY) ENGINE=InnoDB;
 
 SET GLOBAL wsrep_provider_repl_max_ws_size=1;

mysql-test/suite/wsrep/t/wsrep_provider_plugin_basic.test

 --source include/have_wsrep.inc
 --source include/have_innodb.inc
 
+--let $galera_version=26.4.14
+source include/check_galera_version.inc;
 
 #
 # Test string option

mysql-test/suite/wsrep/t/wsrep_provider_plugin_defaults.test

 --source include/have_wsrep.inc
 --source include/have_innodb.inc
 
+--let $galera_version=26.4.14
+source include/check_galera_version.inc;
+
 SELECT COUNT(*) FROM INFORMATION_SCHEMA.GLOBAL_VARIABLES WHERE VARIABLE_NAME LIKE 'wsrep_provider%';
 
 --vertical_results

mysql-test/suite/wsrep/t/wsrep_provider_plugin_wsrep_off.cnf

+# Use default setting for mysqld processes
+!include include/default_mysqld.cnf
+
+[mysqld]
+wsrep-on=OFF
+
+[mysqld.1]
+wsrep-on=OFF
+#galera_port=@OPT.port
+#ist_port=@OPT.port
+#sst_port=@OPT.port
+plugin-wsrep-provider=ON

mysql-test/suite/wsrep/t/wsrep_provider_plugin_wsrep_off.test

+--source include/have_wsrep.inc
+--source include/have_innodb.inc
+
+SELECT @@wsrep_on;
+
+select variable_type, global_value from information_schema.system_variables where variable_name = 'wsrep_provider%';

sql/wsrep_plugin.cc

@@ -34,6 +34,7 @@
 #include "wsrep_server_state.h"
 #include "wsrep_var.h" // wsrep_refresh_provider_options()
 
+#ifdef WITH_WSREP
 static bool provider_plugin_enabled= false;
 
 /* Prototype for provider system variables */
@@ -277,12 +278,10 @@ static int wsrep_provider_plugin_init(void *p)
 {
   WSREP_DEBUG("wsrep_provider_plugin_init()");
 
-  if (!WSREP_ON_ || !wsrep_provider ||
-      (wsrep_provider && !strncasecmp(wsrep_provider, WSREP_NONE, FN_REFLEN)))
+  if (!WSREP_ON)
   {
-	  WSREP_ERROR("plugin-wsrep-provider can't be enabled if wsrep_on==OFF or wsrep_provider is unset or set to 'none'");
-	  my_message(ER_WRONG_ARGUMENTS, "plugin-wsrep-provider can't be enabled if wsrep_on==OFF or wsrep_provider is unset or set to 'none'", MYF(0));
-	  return 1;
+    sql_print_information("Plugin '%s' is disabled.", "wsrep-provider");
+    return 0;
   }
 
   provider_plugin_enabled= true;
@@ -369,3 +368,5 @@ maria_declare_plugin(wsrep)
   MariaDB_PLUGIN_MATURITY_STABLE     /* Maturity */
 }
 maria_declare_plugin_end;
+
+#endif /* WITH_WSREP */