Support dynamic enable/disable of Log Correlation Feature

With the introduction of log correlation feature, each log statement emitted by code carrying a valid span will usually have 4-5 additional fields facilitating the correlation of logs generated by same execution flow. This data may be annoying for someone not looking for any log correlation.

Hence, introduce following voltctl log sub-commands to support dynamically changing the log-correlation feature for voltha components. Component should reflect the changes instantly and stop outputting the additional fields in log statements if log correlation has been disabled for that component.

Enable log-correlation for a specific component

voltctl log correlation enable <component-name>

Enable log-correlation for all components

voltctl log correlation enable

Disable log-correlation for a specific component

voltctl log correlation disable <component-name>

List log-correlation status all components (can also use show sub-command)

voltctl log correlation list