Pass Context down the execution call hierarchy across voltha codebase

In order to support propagation of Span Context down the execution path, modify voltha components to change function signatures to add context.Context as the first parameter (if not already present) in all the methods which are performing logging and hence needs the context.

Ensure the variable name used across for this parameter is ‘ctx’.

Also, set logger variable to CLogger instance in common.go and modify the logger statements to use new Context Aware logger.