[crm] add crm config clear cli command

[AmitKaushik7]

- What I did
Added the "crm config clear" cli command to remove the polling interval configured and remove the threshold settings configured.

- How I did it
Added crm config clear command in crm/main.py by deleting the deleting the CRM table from the config DB.

- How to verify it
Default:
crm show thresholds all => Error: will show empty table at reset
crm show summary => Error! could not get CRM configuration
Configure Polling interval and CRM threshold for any resource (say fdb)
crm config polling interval 10
crm config thresholds fdb type percentage
crm config thresholds fdb low 10
crm config thresholds fdb high 60
Verify the config
crm show thresholds all => Will show the configure Thresholds entries for FDB
crm show summary => Will show Polling interval as 10 second(s)
Execute Clear command
crm config clear
Verify the config
crm show thresholds all => Error: will show empty table at reset
crm show summary => Error! could not get CRM configuration

- Previous command output (if the output of a command-line utility has changed)
NA- no change in the format of the output.
- New command output (if the output of a command-line utility has changed)
NA
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[AmitKaushik7]

CI:Rerun

[AmitKaushik7]

CI:rerun

[jleveque]

Retest this please

[prsunny]

Why do we need this change? Also this is an unsupported operation for CRM Orch. The current support is only to set config values and not delete config.

[AmitKaushik7]

Agreed. This is an enhancement and useful in automation scripts to undo the CRM Threshold config.