Clean up kernel code (#2898)

1) Fix memory leak of callback head in allowlist.c
2) Remove duplicated logic and incorrect log in kernel_umount.c
3) Prevent sleep in kprobe context in ksud.c
4) Remove useless is_unsupported_uid, use euid for security enhance,
   add FIXME in setuid_hook.c
5) Remove useless fd argument for execve hook, fix incorrent pointer
   usage in syscall_hook_manager.c and sucompat.c
6) Use correct errno in supercalls.c

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Co-authored-by: Ylarod <me@ylarod.cn>

kernel/kernel_umount.c

@@ -135,8 +135,6 @@ int ksu_handle_umount(uid_t old_uid, uid_t new_uid)
 
     if (!ksu_uid_should_umount(new_uid)) {
         return 0;
-    } else {
-        pr_info("uid: %d should not umount!\n", current_uid().val);
     }
 
     // check old process's selinux context, if it is not zygote, ignore it!