proxy: Add documentation on how to display log messages
proxy: Add documentation on how to display log messages

cc-proxy just gained log messages. Document how one can enable them.

Signed-off-by: Damien Lespiau <64bd3cb94f359c1a3ce68dae5e26b40578526277@intel.com>

dlespiau/clearcontainers-proxy,dlespiau/proxy,dlespiau/proxy,dlespiau/clearcontainers-proxy,clearcontainers/proxy,clearcontainers/proxy