rpl_slave_status failed on pushbuild. The slave stopped with an
error. Adding sync_slave_with_master fixes the problem. Updated
test case. 

mysql-test/suite/rpl/r/rpl_slave_status.result:
  Updated result file.
mysql-test/suite/rpl/t/rpl_slave_status.test:
  - Added comment explaining what the test does.
  - Added sync_slave_with_master in two places where it was missing. This
    caused sporadic pushbuild errors.
  - Added wait_for_slave_to_{start,stop} after {START,STOP} SLAVE queries.
  - Removed 'drop table if exists' from setup code.
  - Replaced save_master_pos;connection slave;sync_with_master by
    sync_slave_with_master.
  - Replaced 'delete from mysql.user' by 'drop user'.
  - Wrapped 'show slave status' inside query_get_value(), so that only what
    we test is in the output.