Fix sporadic test failure of mariabackup.slave_provision_nolock

The test requires a larger innodb log file size; this was lost as a
side-effect of d7699c51.
Signed-off-by: Kristian Nielsen <knielsen@knielsen-hq.org>

mysql-test/suite/mariabackup/slave_provision_nolock.cnf

@@ -3,6 +3,9 @@
 [mysqld.1]
 log-slave-updates
 loose-innodb
+# Test does a lot of DML during the backup, larger than 10M log is needed for
+# mariabackup to always be able to copy all that it needs.
+loose-innodb_log_file_size=       96M
 
 [mysqld.2]
 log-slave-updates