Affected tests fixing. After the fix for st_relay_log_info::wait_for_pos() that
handles widely used select('master-bin.xxxx',pos) invoked by mysqltest
there appeared to be four tests that either tried synchronizing when
the slave was stopped or used incorrect synchronization method like
to call `sync_with_master' from the current connection being to the
master itself.

Fixed with correcting the current connection or/and using the correct
synchronization macro when possible.