not use sub process to fetch mmdb

[rogeryk]

I find some warning log when i run systemctl --user start clash

clash.service: Found left-over process 2868 (python3) in control group while starting unit. Ignoring.
This usually indicates unclean termination of a previous run, or service implementation deficiencies

The clash server config ExecStartPre=/usr/bin/clashup --pre
and I find clashup script which use daemon to fetch mmdb. It will create a sub process.

if self.config.get('mmdb_version_url') and self.config.get('mmdb_file_url'):
    with daemon.DaemonContext():
        self.update_mmdb()

When I removed the mmdb configuration, it was just fine. And I find
https://www.freedesktop.org/software/systemd/man/systemd.service.html

Note that ExecStartPre= may not be used to start long-running processes. All processes forked off by processes invoked via ExecStartPre= will be killed before the next service process is run.

Maybe it should be deleted here.