fix typo command/agent/monitor/monitor.go
Co-Authored-By: Chris Baker <1675087+cgbaker@users.noreply.github.com>

Update command/agent/monitor/monitor.go
Co-Authored-By: Chris Baker <1675087+cgbaker@users.noreply.github.com>

address feedback, lock to prevent send on closed channel

fix lock/unlock for dropped messages