recvmmsg01: Use exit()

exit() flush open streams, therefore should be used unless
exit in signal handlers (exit() is not async-signal-safe).

Fixes: 1d4d5a0 ("recvmmsg01: Workaround segfault on libc variant on 32 bit")
Signed-off-by: Petr Vorel <[email protected]>

testcases/kernel/syscalls/recvmmsg/recvmmsg01.c

@@ -97,7 +97,7 @@ static void test_bad_addr(unsigned int i)
 	pid = SAFE_FORK();
 	if (!pid) {
 		verify_recvmmsg(i, timeout);
-		_exit(0);
+		exit(0);
 	}
 
 	SAFE_WAITPID(pid, &status, 0);