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/supercalls.c

@@ -361,7 +361,7 @@ static int do_set_feature(void __user *arg)
 
 static int do_get_wrapper_fd(void __user *arg) {
     if (!ksu_file_sid) {
-        return -1;
+        return -EINVAL;
     }
 
     struct ksu_get_wrapper_fd_cmd cmd;