MDEV-18379: Unification of check for IPv6

Currently, the three-node mtr suite for Galera (galera_3nodes)
uses a separate IPv6 availability check using the "have_ipv6.inc"
file. This check duplicates a more accurate check at suite.pm
level, which can be used by including the file "check_ipv6.inc".

This patch removes this discrepancy between suites. In addition,
one of the files in the galera_3nodes suite does not contain the
option "--bind-address=::" which is needed for the test to work
correctly with IPv6 (at least on some systems), since without
it the server will not wait for connections on the IPv6 interface.

https://jira.mariadb.org/browse/MDEV-18379

mysql-test/suite/galera_3nodes/include/have_ipv6.inc

-# Check if ipv6 is available.
-#
---disable_query_log
---disable_result_log
-connect (checkcon123456789,::1,root,,test);
-if($mysql_errno)
-{
-    skip No IPv6 support;
-}
-connection default;
-disconnect checkcon123456789;
---enable_result_log
---enable_query_log
-# end check
-

mysql-test/suite/galera_3nodes/r/GAL-501.result

@@ -4,9 +4,12 @@ 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

mysql-test/suite/galera_3nodes/t/GAL-501.opt

+--bind-address=::

mysql-test/suite/galera_3nodes/t/GAL-501.test

@@ -5,7 +5,7 @@
 # ist.recv_addr=[::1]
 
 --source include/galera_cluster.inc
---source include/have_ipv6.inc
+--source include/check_ipv6.inc
 
 # Confirm that initial handshake happened over ipv6
 

mysql-test/suite/galera_3nodes/t/galera_ipv6_mariabackup.test

 --source include/galera_cluster.inc
---source include/have_ipv6.inc
+--source include/check_ipv6.inc
 --source include/have_mariabackup.inc
 
 # Confirm that initial handshake happened over ipv6

mysql-test/suite/galera_3nodes/t/galera_ipv6_mysqldump.test

 --source include/galera_cluster.inc
---source include/have_ipv6.inc
+--source include/check_ipv6.inc
 
 call mtr.add_suppression("WSREP: wsrep_sst_method is set to 'mysqldump' yet mysqld bind_address is set to'");
 call mtr.add_suppression("Failed to load slave replication state from table mysql.gtid_slave_pos");

mysql-test/suite/galera_3nodes/t/galera_ipv6_rsync.test

 --source include/galera_cluster.inc
---source include/have_ipv6.inc
+--source include/check_ipv6.inc
 
 # Confirm that initial handshake happened over ipv6