proxy: Associate a unique ID to clients
proxy: Associate a unique ID to clients

I'd like to be able to identify clients to easily differentiate them.
The first use will be in debug/trace messages to track which client is
doing what.

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

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