This patch makes two changes:

* It replaces `--sleep 1` with appropriate wait_conditions, and
  removes another `--sleep 1` which is no longer necessary, after
  MDEV-14144 has been fixed.

* It moves the `RESET MASTER` from node_1 at the very end, when it
  it sure that the other nodes have applied the the final cleanup
  `DROP TABLE t1,t2.`
  This solves the problem with the `DROP TABLE` not being replicated
  to the asynchronous slaves, which would make the test fail with:
  `Timeout in wait_condition.inc for SELECT COUNT(*) = 0 FROM INFORMATION_SCHEMA.TABLES WHERE TABLE_NAME = 't1';`