syscalls/sysctl03: Change TWARN to TINFO.

The TWARN is propagated to the test return value
and interpreted as a test (internal) failure,
moreover the rest of the testcases seems to
use TWARN this way.

So this replaces TWARN with TINFO which
makes the testcase to PASS.

Signed-off-by: Cyril Hrubis <chrubis@suse.cz>