direct_io/diotest1.c: fix gcc warning and use test temp directory

Unlike other diotests, diotest1 doesn't use temporary directory
for its test files but rather the directory it is run in.

also fix:
* fix old-style definition warning for prg_usage();
* use SAFE_* macros;
* add cleanup().

Signed-off-by: Alexey Kodanev <alexey.kodanev@oracle.com>
Acked-by: Cyril Hrubis <chrubis@suse.cz>
1 file changed