Disable directory polling in default configuration table

[semaldona]

Checklist (Please check before submitting)

• I reviewed the Contributing Guide.
• I reviewed the CF README.md file to see if the feature is in the major future work.
• I performed a cursory search to see if the feature request is relevant, not redundant, nor in conflict with other tickets.

Is your feature request related to a problem? Please describe.
The default configuration table cf_def_config.c enables channel 0 directory polling on /cf/poll_dir at app startup. Unless that directory already exists on the target filesystem, CF will periodically emit the error event 65 message "CF: failed to open playback directory /cf/poll_dir, error=-1". When testing and validating the CF app running defaults, it is not ideal to have unnecessary error events being periodically reported.

Describe the solution you'd like
Disable all directory polling in the default configuration table. Because this feature requires foreknowledge of specific directories resident on the target filesystem, it should only be configured and enabled by end users. All channels should have polling disabled and no polling settings in the CF_PollDir_t structure.

Describe alternatives you've considered
N/A

Additional context
N/A

Requester Info
Sergio Maldonado, NASA GSFC, Arctic Slope Technical Services