sporadic failures of main.bootstrap

give every bootstrap server its own tmpdir, by default it's var/tmp,
which is shared in --parallel

mysql-test/main/bootstrap.test

@@ -7,7 +7,7 @@ drop table if exists t1;
 
 # Add the datadir to the bootstrap command
 let $MYSQLD_DATADIR= `select @@datadir`;
-let $MYSQLD_BOOTSTRAP_CMD= $MYSQLD_BOOTSTRAP_CMD --datadir=$MYSQLD_DATADIR --default-storage-engine=MyISAM --loose-skip-innodb --plugin-maturity=unknown;
+let $MYSQLD_BOOTSTRAP_CMD= $MYSQLD_BOOTSTRAP_CMD --datadir=$MYSQLD_DATADIR --tmpdir=$MYSQL_TMP_DIR --default-storage-engine=MyISAM --loose-skip-innodb --plugin-maturity=unknown;
 #
 # Check that --bootstrap reads from stdin
 #

mysql-test/main/bootstrap_innodb.test

@@ -19,7 +19,7 @@ rollback to savepoint s1;
 insert t1 values (5);
 commit;
 EOF
-exec $MYSQLD_BOOTSTRAP_CMD --datadir=$datadir --innodb < $MYSQLTEST_VARDIR/tmp/bootstrap_test.sql >> $MYSQLTEST_VARDIR/tmp/bootstrap.log 2>&1;
+exec $MYSQLD_BOOTSTRAP_CMD --datadir=$datadir --tmpdir=$MYSQL_TMP_DIR --innodb < $MYSQLTEST_VARDIR/tmp/bootstrap_test.sql >> $MYSQLTEST_VARDIR/tmp/bootstrap.log 2>&1;
 remove_file $MYSQLTEST_VARDIR/tmp/bootstrap_test.sql;
 
 source include/start_mysqld.inc;

mysql-test/suite/mariabackup/big_innodb_log.test

@@ -7,7 +7,7 @@
 --source include/have_debug.inc
 
 --let MYSQLD_DATADIR= `select @@datadir`
-let $MYSQLD_BOOTSTRAP_CMD= $MYSQLD_BOOTSTRAP_CMD --datadir=$MYSQLD_DATADIR --debug-dbug=+d,innodb_small_log_block_no_limit;
+let $MYSQLD_BOOTSTRAP_CMD= $MYSQLD_BOOTSTRAP_CMD --datadir=$MYSQLD_DATADIR --tmpdir=$MYSQL_TMP_DIR --debug-dbug=+d,innodb_small_log_block_no_limit;
 
 --source include/kill_mysqld.inc
 --rmdir $MYSQLD_DATADIR