truncate/truncate03.c: cleanup

Merge truncate03, truncate04 into truncate03 test.
Delete some useless comments.
Use some SAFE_* macros.
Move the test body from main() to truncate_verify().

Signed-off-by: Xing Gu <gux.fnst@cn.fujitsu.com>
truncate/truncate03.c: add EFBIG and ELOOP error value tests

Signed-off-by: Xing Gu <gux.fnst@cn.fujitsu.com>