Fix flaky rpl_binlog_trx_meta_data_multi_table

Summary:
`purge binary logs before now()` is flaky because it depends on time.
Replacing that with `purge binary logs to $binlog`.

Squash with D10120351

Reviewed By: yashtc

Differential Revision: D10185280

fbshipit-source-id: c65c6c7

mysql-test/suite/rpl/r/rpl_binlog_trx_meta_data_multi_table.result

@@ -12,9 +12,9 @@ insert into t1 values();
 insert into t2 values();
 insert into t2 values();
 flush logs;
-purge binary logs before now();
+purge binary logs to 'binlog';
 flush logs;
-purge binary logs before now();
+purge binary logs to 'binlog';
 delete t1, t2 from t1, t2;
 flush logs;
 "There should be only one rows_query event in master binlog"

mysql-test/suite/rpl/t/rpl_binlog_trx_meta_data_multi_table.test

@@ -18,11 +18,15 @@ sync_slave_with_master;
 # start a fresh binlog
 connection master;
 flush logs;
-purge binary logs before now();
+let $binlog= query_get_value(SHOW MASTER STATUS, File, 1);
+replace_result $binlog binlog;
+eval purge binary logs to '$binlog';
 
 connection slave;
 flush logs;
-purge binary logs before now();
+let $binlog= query_get_value(SHOW MASTER STATUS, File, 1);
+replace_result $binlog binlog;
+eval purge binary logs to '$binlog';
 
 # multi-table statement, there should only be one rows_query event for this
 connection master;