Improve coverage

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Files to work on:

• [ ] acl.py
• [ ] conf_manager.py
• [ ] credentials.py
• [x] file_monitor.py #127
• [ ] hec_config.py
• [ ] log.py
• [x] net_utils.py #120
• [ ] orphan_process_monitor.py
• [x] pattern.py
• [ ] server_info.py
• [ ] splunk_rest_client.py
• [ ] splunkenv.py
• [x] time_parser.py #120
• [ ] timer_queue.py
• [ ] user_access.py
• [ ] utils.py
• [x] modular_input.checkpointer #122
• [ ] modular_input.event
• [ ] modular_input.event_writer
• [ ] modular_input.modular_input