write()/read()

Sometimes stop/restart master or stop/restart salve can cause
network error, which can cause the 'invalid file descriptor
-1 in syscall write()/read()' warnings. All involved test
cases except rpl_slave_load_remove_tmpfile belong to the
kind of network error. So they are expected.
The 'rpl_slave_load_remove_tmpfile' belongs to file error,
but it is testing the file error as following code:
DBUG_EXECUTE_IF("remove_slave_load_file_before_write",
my_close(fd,MYF(0)); fd= -1; my_delete(fname, MYF(0)););
So it's expected too.

To fix the problem, add the valgrind warnings to the global
suppression list to suppress it.