--innodb command line option causes mariabackup to fail

After MDEV-24197, all mtr tests for Galera failed during SST because mariabackup fails with the following diagnostic:

Info: Using unique option prefix 'innodb' is error-prone and can break in the future. Please use the full name 'innodb-force-recovery' instead.

210402 03:24:30 innobackupex: Starting the backup operation

There new option added by MDEV-24197 is the only argumentin the list (in "innobackupex.cc") that starts with "--innodb" prefix. As a result, get_opt treats any argument starting with "--innodb-" as shorthand for "--innodb-force-recovery".
And we get a non-zero xtrabackup_innodb_force_recovery value due to the parser's erroneous interpretation of some other argument (some other option with the "--innodb-" prefix) supposedly as "--innodb-force-recovery".
In particular, this has to do with the bootstrap process when starting mtr - it's from /mysql-test/t/bootstrap_innodb.test:

exec $MYSQLD_BOOTSTRAP_CMD --datadir=$datadir --innodb < $MYSQLTEST_VARDIR/tmp/bootstrap_test.sql >> $MYSQLTEST_VARDIR/tmp/bootstrap.log 2>&1;