systemd: Fix a failure in systemd-sysctl during a startup of systemd-236

[codesnake]

Backport a patch to fix a failure in systemd-sysctl during a startup of systemd-236.

On WeTek Hub and WeTek Play 2 systemd-sysctl fails to start with the following errors:

Jan 01 02:00:22 LibreELEC systemd-sysctl[2665]: Couldn't write '1' to 'fs/protected_hardlinks': Input/output error
Jan 01 02:00:22 LibreELEC systemd-sysctl[2665]: Couldn't write '1' to 'fs/protected_symlinks': Input/output error
Jan 01 02:00:22 LibreELEC systemd-sysctl[2665]: Couldn't write '0' to 'dev/cdrom/lock': Input/output error
Jan 01 02:00:22 LibreELEC systemd-sysctl[2665]: Couldn't write '0' to 'dev/cdrom/autoclose': Input/output error
Jan 01 02:00:22 LibreELEC systemd-sysctl[2665]: Couldn't write '16384' to 'vm/min_free_kbytes': Input/output error
Jan 01 02:00:22 LibreELEC systemd-sysctl[2665]: Couldn't write '1' to 'net/ipv4/tcp_no_metrics_save': Input/output error
Jan 01 02:00:22 LibreELEC systemd-sysctl[2665]: Couldn't write '10' to 'vm/swappiness': Input/output error
Jan 01 02:00:22 LibreELEC systemd[1]: systemd-sysctl.service: Main process exited, code=exited, status=1/FAILURE
Jan 01 02:00:22 LibreELEC systemd[1]: systemd-sysctl.service: Failed with result 'exit-code'.
Jan 01 02:00:22 LibreELEC systemd[1]: Failed to start Apply Kernel Variables.

The patch in this PR fixes the issue.

[Ray-future]

Thank you

[codesnake]

Thanks @HiassofT for finding the roots of the issue and a fix for it.