syscalls/accept4: Fix test when accept4 returns ENOSYS

* Make the test actually exit with TCONF when accept4 returned ENOSYS

* Remove ifdefs around the main as due tu linux_syscall_numbers.h
  both __NR_accept4 and __NR_socketcall are always defined.

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