MDEV-28204: The tr utility does not work as expected on rsync SST

This commit contains a fix to use modern syntax for selecting
character classes in the tr utility options.

Also one of the tests for SST via rsync (galera_sst_rysnc2) is made
more reliable (to avoid rare failures during automatic testing).

mysql-test/suite/galera/t/galera_sst_rsync2.cnf

@@ -5,10 +5,10 @@ wsrep_sst_method=rsync
 
 [mysqld.1]
 wsrep_provider_options='base_port=@mysqld.1.#galera_port;gcache.size=1;pc.ignore_sb=true'
-log_bin=@ENV.MYSQLTEST_VARDIR/server1_binlog
+log_bin=@ENV.MYSQLTEST_VARDIR/mysqld.1/server1_binlog
 log_bin_index=@ENV.MYSQLTEST_VARDIR/tmp/server1_binlog_index.index
 
 [mysqld.2]
 wsrep_provider_options='base_port=@mysqld.2.#galera_port;gcache.size=1;pc.ignore_sb=true'
-log_bin=@ENV.MYSQLTEST_VARDIR/server2_binlog
+log_bin=@ENV.MYSQLTEST_VARDIR/mysqld.2/server2_binlog
 log_bin_index=@ENV.MYSQLTEST_VARDIR/tmp/server2_binlog_index.index

mysql-test/suite/galera/t/galera_sst_rsync2.test

@@ -7,6 +7,8 @@
 --source suite/galera/include/galera_st_shutdown_slave.inc
 --source suite/galera/include/galera_st_clean_slave.inc
 
+--let $wsrep_recover_additional=--log-bin=$MYSQLTEST_VARDIR/mysqld.2/server2_binlog --log-bin-index=$MYSQLTEST_VARDIR/tmp/server2_binlog_index.index
+
 --source suite/galera/include/galera_st_kill_slave.inc
 --source suite/galera/include/galera_st_kill_slave_ddl.inc
 --source include/auto_increment_offset_restore.inc

scripts/wsrep_sst_mariabackup.sh

@@ -472,7 +472,7 @@ read_cnf()
 
     encrypt=$(parse_cnf "$encgroups" 'encrypt' 0)
     tmode=$(parse_cnf "$encgroups" 'ssl-mode' 'DISABLED' | \
-            tr [:lower:] [:upper:])
+            tr '[[:lower:]]' '[[:upper:]]')
 
     case "$tmode" in
     'VERIFY_IDENTITY'|'VERIFY_CA'|'REQUIRED'|'DISABLED')

scripts/wsrep_sst_rsync.sh

@@ -224,7 +224,7 @@ SSTCERT="$tpem"
 SSTCA="$tcert"
 SSTCAP="$tcap"
 
-SSLMODE=$(parse_cnf "$encgroups" 'ssl-mode' | tr [:lower:] [:upper:])
+SSLMODE=$(parse_cnf "$encgroups" 'ssl-mode' | tr '[[:lower:]]' '[[:upper:]]')
 
 if [ -z "$SSLMODE" ]; then
     # Implicit verification if CA is set and the SSL mode