Update conmon to 2.1.0
Changes:
- Bug fixes:
- logging: buffer partial messages to journald
- exit: close all fds >= 3
- fix: cgroup: Free memory_cgroup_file_path if open fails. Call g_free instead of free.
- Make libdl optional in meson definition
- Avoid mainfd_std{in,out} sharing the same file descriptor.
- exit_command: unset subreaper attribute before running exit command
- conmon: free userdata files before exec cleanup
- Features:
- logging: new mode -l passthrough
- ctr_logs: use container name or ID as SYSLOG_IDENTIFIER for journald