MDEV-23574 : galera_3nodes.galera_ipv6_mariabackup_section MTR failed…

…: Could not open '../galera/include/have_mariabackup.inc'

Fix the include and add force_restart to stabilize.

mysql-test/suite/galera_3nodes/r/galera_ipv6_mariabackup_section.result

@@ -4,15 +4,20 @@ VARIABLE_VALUE LIKE '%[::1]%'
 SELECT VARIABLE_VALUE = 3 FROM INFORMATION_SCHEMA.GLOBAL_STATUS WHERE VARIABLE_NAME = 'wsrep_cluster_size';
 VARIABLE_VALUE = 3
 1
+connection node_2;
 SET GLOBAL wsrep_provider_options='gmcast.isolate=1';
+connection node_1;
 CREATE TABLE t1 (f1 INTEGER) ENGINE=InnoDB;
 INSERT INTO t1 VALUES (1);
+connection node_2;
 SET GLOBAL wsrep_provider_options='gmcast.isolate=0';
 SELECT COUNT(*) = 1 FROM t1;
 COUNT(*) = 1
 1
 DROP TABLE t1;
+connection node_1;
 include/assert_grep.inc [Streaming the backup to joiner at \[::1\]]
 include/assert_grep.inc [async IST sender starting to serve tcp://\[::1\]:]
+connection node_2;
 include/assert_grep.inc [IST receiver addr using tcp://\[::1\]]
 include/assert_grep.inc [Prepared IST receiver, listening at: tcp://\[::1\]]

mysql-test/suite/galera_3nodes/t/galera_ipv6_mariabackup_section.test

@@ -1,7 +1,8 @@
 --source include/galera_cluster.inc
 --source include/check_ipv6.inc
 --source include/have_innodb.inc
---source ../galera/include/have_mariabackup.inc
+--source include/have_mariabackup.inc
+--source include/force_restart.inc
 
 # Confirm that initial handshake happened over ipv6