telemetry: add default callback commands
telemetry: add default callback commands

The default commands are now added to provide the list of commands
available, help text for a specified command, and also information
about DPDK and telemetry.

Signed-off-by: Ciara Power <2dd8f648091a527a3f34edd30b226be01da76a0e@intel.com>
Signed-off-by: Bruce Richardson <66b9e8e8fbd5e9f41f91b0af050876182ce9d0e4@intel.com>
Reviewed-by: Keith Wiles <f97a07384723981b442bf4ce37d40edbfd008094@intel.com>

john-mcnamara-intel/dpdk,john-mcnamara-intel/dpdk,john-mcnamara-intel/dpdk,john-mcnamara-intel/dpdk